• Overview of a Computer System
• SS1 Computer Science First Term: History of Computer
• History of computer II
• Input Devices
• Basic Functions and Uses of Computer
• Basic Computer Language
• COMPUTER HARDWARE AND SOFTWARE: SS1 FIRST TERM COMPUTER SCIENCE
• SS1 Computer Science First Term: Computer Output Devices
• OUTPUT DEVICES (PRINTER): SS1 FIRST TERM COMPUTER SCIENCE

Overview of a Computer System

Computer Science SS1 First Term

Week 1

Topic: Overview of a Computer System

Contents:

What is a computer?

Constituents of a computer

Characteristics of a computer

What is a Computer?

A computer is a mechanical programs machine that accepts data as input, store and manipulates the data through instructions in order to give output as information.

A Computer is an electronic device known to be a very powerful tool for processing data into meaning information in a faster, neater and cheaper form. The Computer System is one that is able to take a set of inputs, process them and create a set of outputs.

A Computer is a general-purpose device that can be programmed to carry out a set of arithmetic or logical operations automatically. Since a sequence of operations can be readily changed, the computer can solve more than one kind of problem. Conventionally, a computer consists of at least one processing element, typically a central processing unit (CPU), and some form of memory.

An INPUT consists of data or commands that are entered into the computer usually via an input device such as keyboard, mouse, scanner e.t.c. The role of an input is to provide data for further processing.

Processing is the stage where the input data is manipulated to produce meaningful information. Processing can include a number of stages, sorting, searching, calculating, graphing e.t.c The result obtained is called output.

An OUTPUT is the stage where information received via processing is presented to the user in suitable format. Most outputs involve converting digital data to a physical effect which a person can see or hear. You might be able to see your output via a print out or a display and also hear via music, voice training instructions.

Constituents of a Computer

The computer system has two main parts namely

1. Computer hardware
2. Computer software

Computer hardware: This refers to the physical things of a computer, things that can be seen, touched and handled. Example – the system unit and peripherals.

1. The system unit: This is the combination of the major parts of the computer which includes CPU, mother board, RAM, ROM, chipsets, power module, CMOS battery e.t.c
2. The peripherals: These are hardware parts used to enhance the capabilities of the computer or improve its performance. E.g keyboard, mouse, joystick, light pen, scanner, monitor, speaker, printer e.t.c

 

Computer software: Is a set of instructions or programs that direct the operation of the computer and devices attached to it. Computer software is any set of machine-readable instructions that directs a computer’s processor to perform specific operations. Computer software contrasts with computer hardware, which is the physical component of computers. 

The computer software can be divided into two – the system software and the application software.

1. System software: These are software used in performing basic tasks in order to manage a computer system. E.g. windows 95, 98, 2000, xp, vista, Windows 8, linux , computer antivirus, basic input-output systems, device drivers.
2. Application software: These are software used to perform specific task, processing data in the computer. Application software uses the computer system to perform special functions or provide entertainment functions beyond the basic operation of the computer itself. There are many different types of application software, because the range of tasks that can be performed with a modern computer is so largeE.g Ms word – for typing documents, Ms Excel – For accounting, Adobe photoshop – for editing pictures, Corel draw – for graphics designing, Ms powerpoint – For slide presentations.
3. Malicious software or malware – They are computer programs developed to harm and disrupt computers. As such, malware is undesirable. Malware is closely associated with computer-related crimes, though some malicious programs may have been designed as practical jokes.

Characteristics of a Computer

1. Accuracy and precision
2. High speed of operation
3. Reliability
4. Versatility
5. Automation
6. Speed
7. Storage.

ASSESSMENT.

1. Explain the term “Computer Hardware”.
2. Explain the term “Computer Software”.
3. What are the components of computer hardware?
4. List three output services.

SS1 Computer Science First Term: History of Computer

Topic: History of Computer

The development of the first counting device has been dated to ancient times, a man called abacus used a counting device about 3000 years ago and from this time and man has continued to improve. Ancient methods of counting were through the use of fingers, stones, sticks and grains.

The history of computer science began long before the modern discipline of computer science that emerged in the 20th century, and hinted at in the centuries prior.The progression, from mechanical inventions and mathematical theories towards the modern computer concepts and machines, formed a major academic field and the basis of a massive worldwide industry.

The earliest known tool for use in computation was the abacus, developed in period 2700–2300 BCE in Summer . The Sumerians’ abacus consisted of a table of successive columns which delimited the successive orders of magnitude of their sexagesimal number system. Its original style of usage was by lines drawn in sand with pebbles. Abaci of a more modern design are still used as calculation tools today

Charles Babbage is described as the ‘Father of Computer’. Charles Babbage, an English mechanical engineer and polymath, originated the concept of a programmable computer. Considered the “father of the computer”, he conceptualized and invented the first mechanical computer in the early 19th century. After working on his revolutionary difference engine, designed to aid in navigational calculations, in 1833 he realized that a much more general design, an Analytical Engine, was possible. The input of programs and data was to be provided to the machine via punched cards, a method being used at the time to direct mechanical looms such as the Jacquard loom. For output, the machine would have a printer, a curve plotter and a bell. The machine would also be able to punch numbers onto cards to be read in later. The Engine incorporated an arithmetic logic unit, control flow in the form of conditional branching and loops, and integrated memory, making it the first design for a general-purpose computer that could be described in modern terms as Turing-complete.

Mechanical devices

1. Abacus: It is the earliest form of computing system and was produced by the Chinese in the early age. It is made up of a frame, iron and beads in between them. They are used for counting and calculating. Also functions in adding and subtracting.
2. Slide rule: This is used for performing operation which involves multiplication and division.

Slide rule

Abacus

Electronic devices

1. Pascal’s calculating machine: Blaise Pascal invented a hand operated calculator. This was operated by turning dials.
2. Charles Babbage: He was credited for the invention of modern computer and he was also called the Father of Computer. The machines he invented are called the “difference machine” and the ‘Analyte machine’. In 1930, he used these machines to solve mathematical equations.

charles babbage Analyte machine

Pascal’s calculating machine

The various generations of computers are listed below

(i) First Generation (1946-1954): In 1946 there was no ‘best’ way of storing instructions and data in a computer memory. There were four competing technologies for providing computer memory: electrostatic storage tubes, acoustic delay lines (mercury or nickel), magnetic drums (and disks?), and magnetic core storage.

The digital computes using electronic valves (Vacuum tubes) are known as first generation computers. The first ‘computer’ to use electronic valves (i.e. vacuum tubes). The high cost of vacuum tubes prevented their use for main memory. They stored information in the form of propagating sound waves.

The vacuum tube consumes a lot of power. The Vacuum tube was developed by Lee DeForest in 1908. These computers were large in size and writing programs on them was difficult. Some of the computers of this generation were: Mark I (electro-mechanical computer) built in 1944, ENIAC (First general purpose electronic computer) built in 1946, EDVAC (binary serial computer) built in 1950, EDSAC (first stored-program computer) built in 1949, UNIVAC (First Commercial Computer) built in 1951.

Other Important Computers of First Generation

Some other computers of this time worth mentioning are the Whirlwind, developed at Massachussets Institute of Technology, and JOHNNIAC, by the Rand Corporation. The Whirlwind was the first computer to display real time video and use core memory. The JOHNNIAC was named in honor of Jon Von Neumann. Computers at this time were usually kept in special locations like government and university research labs or military compounds.

Limitations of First Generation Computer

Followings are the major drawbacks of First generation computers-

1.  They used valves or vacuum tubes as their main electronic component.

2. They were large in size, slow in processing and had less storage capacity.

3.  They consumed lots of electricity and produced lots of heat.

4.  Their computing capabilities were limited.

5. They were not so accurate and reliable.

6.  They used machine level language for programming.

7.  They were very expensive.

Example: ENIAC, UNIVAC, IBM 650 etc

ENIAC – Electronic Numerical Integrator and Calculator/Computer: This was developed by John Mauchly and J. Presper Eckert at the school of engineering of the university of Pennsylvania in 1946. It was the prototype from which most other modern computers evolved. ENIAC contained 17,648 vacuum tubes, 7,200 crystal diodes, 7,000 resistors, 1,500 relay, 10,000 capacitors and 60,000 manual switches and consumed 150watts of power. It has thirty separate unit power supply and forced air cooling. ENIAC also had a functioning unit that was equipped with local program control circuits and store a minimum of twenty 10digit decimal number. It uses card reader for input, card punch for output and the 1500 associated relays. ENIAC is used for arithmetic operations and to calculate the trajectory of artillery shells.

Eniac computer

UNIVAC – Universal Automatic Computer:  This was the world’s first commercially available computer developed by the same designers of ENIAC. It was used for general purpose computing with large amounts of input, output and storage capacity compared to earlier machines. UNIVAC was the first computer to come equipped with a magnetic tape unit and it is also the first computer to use buffer memory. It contains 5600 tubes, 18000 crystal diodes and 300 relays, internal storage capacity of 100 words or 1200 characters.

Univac Computer

(ii)  Second Generation (1955-1964): The second-generation computer used transistors for CPU components & ferrite cores for main memory & magnetic disks for secondary memory. They used high-level languages such as FORTRAN (1956), ALGOL (1960) & COBOL (1960 – 1961). I/O processor was included to control I/O operations.

Around 1955 a device called Transistor replaced the bulky Vacuum tubes in the first generation computer. Transistors are smaller than Vacuum tubes and have higher operating speed. They have no filament and require no heating. Manufacturing cost was also very low. Thus the size of the computer got reduced considerably.

It is in the second generation that the concept of Central Processing Unit (CPU), memory, programming language and input and output units were developed. The programming languages such as COBOL, FORTRAN were developed during this period. Some of the computers of the Second Generation were

1. IBM 1620: Its size was smaller as compared to First Generation computers and mostly used for scientific purpose.

2. IBM 1401: Its size was small to medium and used for business applications.

3. CDC 3600: Its size was large and is used for scientific purposes.

Features:

1.  Transistors were used instead of Vacuum Tube.

2.  Processing speed is faster than First Generation Computers (Micro Second)

3.  Smaller in Size (51 square feet)

4. The input and output devices were faster.

Example: IBM 1400 and 7000 Series, Control Data 3600 etc.

IBM 7000

History of computer II

Computer Science SS1 First Term

Week 3

Topic: History of computer II

(iii) Third Generation (1964-1977) : By the development of a small chip consisting of the capacity of the 300 transistors. These Integrated Circuits (IC) are popularly known as Chips. A single IC has many transistors, registers and capacitors built on a single thin slice of silicon. So it is quite obvious that the size of the computer got further reduced. Some of the computers developed during this period were IBM-360, IBM-370, and VAX-750. Higher level language such as BASIC (Beginners All purpose Symbolic Instruction Code) was developed during this period.  Computers of this generation were small in size, low cost, large memory and processing speed is very high. Very soon ICs Were replaced by LSI (Large Scale Integration), which consisted about 100 components. An IC containing about 100 components is called LSI.

Features:

1. They used Integrated Circuit (IC) chips in place of the transistors.

2. Semi conductor memory devices were used.

3.  The size was greatly reduced, the speed of processing was high, they were   more accurate and reliable.

4.  Large Scale Integration (LSI) and Very Large Scale Integration (VLSI) were also developed.

5.  The mini computers were introduced in this generation.

6. They used high level language for programming.

Example: IBM 360, IBM 370 etc.

(iv)     Fourth Generation : An IC containing about 100 components is called LSI (Large Scale Integration) and the one, which has more than 1000 such components, is called as VLSI (Very Large Scale Integration). It uses large scale Integrated Circuits (LSIC) built on a single silicon chip called microprocessors. Due to the development of microprocessor it is possible to place computer’s central processing unit (CPU) on single chip. These computers are called microcomputers. Later very large scale Integrated Circuits (VLSIC) replaced LSICs. Thus the computer which was occupying a very large room in earlier days can now be placed on a table. The personal computer (PC) that you see in your school is a Fourth Generation Computer Main memory used fast semiconductors chips up to 4 M bits size. Hard disks were used as secondary memory. Keyboards, dot matrix printers etc. were developed. OS-such as MS-DOS, UNIX, Apple’s Macintosh were available. Object oriented language, C++ etc were developed.

Apple’s Macintosh

Features:

1.  They used Microprocessor (VLSI) as their main switching element.

2. They are also called as micro computers or personal computers.

3.  Their size varies from desktop to laptop or palmtop.

4.  They have very high speed of processing; they are 100% accurate, reliable, diligent and versatile.

5.  They have very large storage capacity.

Example: IBM PC, Apple-Macintosh etc.

(v)    Fifth Generation (1991- till date) : 5th generation computers use ULSI (Ultra-Large Scale Integration) chips. Millions of transistors are placed in a single IC in ULSI chips. 64 bit microprocessors have been developed during this period. Data flow & EPIC architecture of these processors have been developed. RISC & CISC, both types of designs are used in modern processors. Memory chips and flash memory up to 1 GB, hard disks up to 600 GB & optical disks up to 50 GB have been developed. fifth generation digital computer will be Artificial intelligence.

ASSESSMENT.

1. Who is the “father of computer”?
2. List and explain the various mechanical and electronic devices you know?
3. What are the limitations of first generation computers?
4. What are the features of the second generation of computers?
5. Which year was the fifth generation computer discovered?

Input Devices

Computer Science SS1 First Term

Week 4

Topic: Input Devices

Input devices are equipment used to get instructions into the computer. It takes in data (facts) and instructions in a suitable form.

Types of input devices

• Keyboard
• Mouse
• Scanner
• Microphone
• Joystick
• Card reader
• Light pen
• Digital camera e.t.c

1. Keyboard: This is the most important input device used when working with a computer. It is used to type instructions that direct the computer on what task to perform. There are four types of keys on the keyboard.

• Function key: These are keys with f1, f2, f3 ….. f12 on the keyboard. They are used to give commands to the computer.
• The alphabetic key: These are the type writer keys (A-Z) on the keyboard. They are used for typing documents, letters and symbols e.t.c
• The numerical keys: The numeric keys contain numbers 0….9.
• The special keys: These include the arrow key, insert key, delete key, home key, backspace key, page up and down, control key and shift key e.t.c

There are two main types of keyboards, the QWERTY keyboard and the enhanced keyboard. The most commonly used keyboard is the QWERTY keyboard.

2. Mouse: The mouse is a pointing device used to give instructions to the computer. It is used to select and move items on the computer screen.

Mouse

Uses of Mouse

• It is used for dragging and dropping.
• It is used for making selections
• It is used to point at objects on the screen.

Types of Mouse

• The mechanical mouse
• Optical mouse
• Opto-mechanical mouse
• Cardless mouse

 3. Light Pen: A light pen is a computer input device in the form of a light-sensitive wand used in conjunction with a computer’s CRT display. It allows the user to point to displayed objects or draw on the screen in a similar way to a touchscreen but with greater positional accuracy.

light pen

    4. Scanner: The scanner provides copy, fax, and scan-to-network capability. A scanner is a digital device that converts films, documents and photographic prints to digital images. A scanner is a device that captures images from photographic prints, posters, magazine pages, and similar sources for computer editing and display.

Scanner

     5. CPU (Central Processing Unit): The brain of the computer. The thing that carries out the tasks you give it. Better CPUs can perform more tasks at once, and perform them faster. That said, not everyone actually takes       advantage of their processor’s full speed, so the high-end models are only really crucial.

CPU

 6. Fan: To keep CPU cool and prevent overheating. A computer fan is any fan inside, or attached to, a computer case used for active cooling, and may refer to fans that draw cooler air into the case from the outside, expel warm air from inside, or move air across a heat sink to cool a particular component.

ASSESSMENT.

1. List the various input devices of a computer system?
2. What are the four types of keys on a keyboard?
3. List the types of mouse you know.
4. What are the functions of a mouse?

Basic Functions and Uses of Computer

Computer Science SS1 First Term

Week 5

Topic: Basic Functions and Uses

Content:

Basic Functions of a Computer

Uses of a Computer

 BASIC FUNCTIONS OF A COMPUTER

All computers, from the smallest hand held computer to the largest supercomputer, perform the same basic functions with digital information. Those functions are:

• Input – Receiving or accepting information from outside sources. The most common way of performing this function is through the information entered through the keyboard and the click of mouse. Typing characters at a keyboard, moving the mouse around the screen or speaking to a computer.
• Output – The results of the processing are made available for use by any user or other devices. The most common ways of producing such outputs are through computer monitor, speakers, and printers. When a computer is connected to other devices, including through Internet, this output is in the form of electrical pulses. Displaying characters or pictures on the screen, printing a research paper, or sending an e-mail message.

• Processing – This is really the core of computer operation. The computer processes the data that is fed to the computer by various means and the data already contained in internal memory to produce the results that is the core of all computer application. E.g. Calculating the square root of a number, sorting a list of names, or producing a three-dimensional image
• Storage – Store information in the computer. The memory is stored in computer in in several different ways depending on how the information is used. For simplicity we will classify in two broad categories. First is the memory in the central processing unit of the computer, and second is the auxiliary memory. The auxiliary memory includes devices such as fixed hard drives. The information stored in computer can also be divided broadly used in two categories. The user data and the instructions used for internal operation and processing in the compute. These instruction are what we call computer programs or software. E.g. Saving your research paper or resume, keeping track of your credit card purchases, or archiving digital pictures of your relatives
• Retrieve – E.g. Recalling a list of addresses or business contacts

USES OF COMPUTER

Computer can be used in all aspects of our everyday lives.

1. Education : Getting the right kind of information is a major challenge as is getting information to make sense. Research shows that computers can significantly enhance performance in learning. Students exposed to the internet say they think the web has helped them improve the quality of their academic research and of their written work. Lots of academic information are available on the internet.
2. Health and Medicine: All medical information and patient records can now be digitized. Software is now able to check the risk of a disease through computer usage. Mental health researchers are using computers to screen troubled teenagers in need of psychotherapy.
3. Defence: a)Computers are used in helping the military find out where all their assets are (Situational Awareness) and in Communications/Battle Management Systems. b) Computers are used in the logistic and ordering functions of getting equipments to and around the battlefield. c) Computers are used in tanks and planes and ships to target enemy forces, help run the platform and more recently to help diagnose any problems with the platforms. d) Computers help design and test new systems.
4. Sports: In today’s technologically growing society, computers are being used in nearly every activity such as recording information, analyzing athlete’s movement, score board e.t.c
5. Government: Various departments of the Government use computer for their planning, control and law enforcement activities. To name a few – Traffic, Tourism, Information & Broadcasting, Education, Aviation and many others.

ASSESSMENT.

1. What are the basic functions of a computer?
2. List and explain the uses of a computer?

Basic Computer Language

Computer Science SS1 First Term

Week 6

Topic: BASIC LANGUAGE

BASIC LANGUAGE/SIMPLE LANGUAGE

A computer language is a special language understood by a computer. It consists of various commands that we give to the computer to do any work.

BASIC (an acronym for Beginner’s All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages whose design philosophy emphasizes ease of use.

A computer language is a set of words, symbols and codes that are used to write a computer program. The process of writing these instructions (program) is called PROGRAMMING. The people who write these programs are called PROGRAMMERS.

Human beings understand a variety of spoken languages (English, Hausa, Igbo and so on) but computer cannot understand these languages. Computer can only understand on language, that is the machine language.

Computer uses machine language to carryout their jobs. This language uses binary digits, 0 and 1, which stand for ‘off and on’ condition of the electric current. It is difficult for the programmer to write the program directly in terms of these digits. So, they write their program in a language called Programming Language.

Programming language code programs in such a manner that the computer can understand them and decode (translate) them into its machine language.

CATEGORIES OF PROGRAMMING LANGUAGE

There are a number of programming languages available nowadays. Some languages are developed for specific computer, other were developed for specific uses, such as scientific or business application.

Programming languages are classified into two major categories.

1. LOW LEVEL LANGUAGE: Low level languages are written to run one particular computer and cannot be easily used on another computer. These languages are difficult for a common programmer to learn

• Machine Language: A machine language is a language directly understood by a computer without any translator. It refers to 0’s and 1’s that the computers understand as instruction. Due to this reason, it is also called a low level language or the first generation language. Writing or coding of programs in the 1s and 0s of machine can be boring and can take a lot of time.
• A machine language program written in assembly language uses a short sequence of letter called mnemonic code like A for addition, C for comparison, L for loading and M for multiplying. As the computer only understands machine languages, you have to convert these mnemonic codes to machine language (0s and 1s). To convert these mnemonic codes into machine language requires the use of translators. An assembler is a program used to translate assembly language into machine language so that the computer can understand it.

2. HIGH LEVEL LANGUAGE: A high level language has the instructions which are similar to English language. It is very user friendly. It is much easier to understand and write with a program using this language. The greatest advantages of these languages are its independence. A program written in HLL can be used on almost all computers without any change. The instructions written in HLL are also converted into machine language with the help of translators. Interpreter and compiler are two program used to translate a high level language into machine language so that the computer can understand it.

• Third generation language: Third generation language uses English –  like words to make it easy for the programmer to write the program. For example, a programmer writes ADD for addition and PRINT for print. Many third generation language also use arithmetic operation such as * for multiplication and + for addition. A third generation program is called source program, which must be translate into machine language before the computer can understand it. Compiler and interpreters are the program used to perform the translation for third generation language. BASIC, COBOL, PASCAL, and FORTRAN are example third generation language.
• Fourth generation language: The fourth generation language also uses English like statement. A fourth generation language is fast and requires much less time and effort on the part of the programmer. In fact, fourth generation language is so easy that the user with very little program background can develop programs while using it. VISUAL BASIC, ORACLE, JAVA e.t.c are example of fourth generation language.
• Natural language: A natural language program does not follow a specific set of rules unlike the fourth generation language. A natural language, sometimes called fifth generation language is a type query language that allows the user to enter request that resembles the speech. Natural languages are often associated with expert system and artificial intelligence.

These systems are popular in the medical field, but are not widely used in business application.

SOME HIGH LEVEL PROGRAMS

1. BASIC: It stands for Beginner’s all purpose symbolic instruction code. It is a programming language used by beginners
2. LOGO: It stands for Language of Graphics Oriented. It is a programming language used to draw different shapes and figure.
3. COBOL: It stands for common business oriented language. This language is specially designed for business application
4. FORTRAN: It stands for ‘Formula Translation’. It is one of the oldest high level languages. This language was designed to solve scientific problems
5. C AND C++: They are the general purpose programming languages popular on minicomputer and microcomputer. They are the most widely used language for developing commercial applications.
6. JAVA: Java is a programming language developed to write programs. It helps in creating games and animation and in developing multimedia effect for the internet.

TYPICAL BASIC KEYWORDS

Data Manipulation

• LET: assigns a value (which may be the result of an expression) to a variable.
• DATA: holds a list of values which are assigned sequentially using the READ command.

Program Flow Control

• IF … THEN … ELSE: used to perform comparisons or make decisions.
• FOR … TO … {STEP} … NEXT: repeat a section of code a given number of times. A variable that acts as a counter is available within the loop.
• WHILE … WEND and REPEAT … UNTIL: repeat a section of code while the specified condition is true. The condition may be evaluated before each iteration of the loop, or after.
• DO … LOOP {WHILE} or {UNTIL}: repeat a section of code Forever or While/Until the specified condition is true. The condition may be evaluated before each iteration of the loop, or after.
• GOTO: jumps to a numbered or labelled line in the program.
• GOSUB: jumps to a numbered or labelled line, executes the code it finds there until it reaches a RETURN Command, on which it jumps back to the operator following the GOSUB – either after a colon, or on the next line. This is used to implement subroutines.
• ON … GOTO/GOSUB: chooses where to jump based on the specified conditions. See Switch statement for other forms.
• DEF FN: a pair of keywords introduced in the early 1960s to define functions. The original BASIC functions were modelled on FORTRAN single-line functions. BASIC functions were one expression with variable arguments, rather than subroutines, with a syntax on the model of DEF FND(x) = x*x at the beginning of a program. Function names were originally restricted to FN+one letter.

Input and Output

• PRINT: displays a message on the screen or other output device.
• INPUT: asks the user to enter the value of a variable. The statement may include a prompt message.
• TAB or AT: sets the position where the next character will be shown on the screen or printed on paper.

Miscellaneous

• REM: holds a programmer’s comment or REMark; often used to give a title to the program and to help identify the purpose of a given section of code.
• USR: transfers program control to a machine language subroutine, usually entered as an alphanumeric string or in a list of DATA statements.
• TRON: turns on a visual, screen representation of the flow of BASIC commands by displaying the number of each command line as it is run. The TRON command, largely obsolete now, stood for, TRace ON. This meant that command line numbers were displayed as the program ran, so that the command lines could be traced. This command allowed easier debugging or correcting of command lines that caused problems in a program. Problems included a program terminating without providing a desired result, a program providing an obviously erroneous result, a program running in a non-terminating loop, or a program otherwise having a non-obvious error.
• TROFF: turns off the display of the number of each command line as command lines run after the command TRON has been used.
• ALT+CTRL+DEL: For re-booting a computer

ASSESSMENT.

1. What is a computer language?
2. The process of writing instructions for the computer is called?
3. List and explain the various categories of programming languages.
4. List and explain the types of High Level programs.

COMPUTER HARDWARE AND SOFTWARE: SS1 FIRST TERM COMPUTER SCIENCE

Computer Hardware/Software

Computer Hardware are the physical elements or the equipment of the computer. Examples include the keyboard, monitor, mouse and the processing unit etc. In other words, Computer Hardware is the physical components of a computer which can be touched and felt. They are  tangible. On the other hand however, Computer Software “is that part of a computer system that consists of data or computer instructions, in contrast to the physical hardware from which the system is built. In computer science and software engineering, computer software is all information processed by computer systems, programs and data. Computer software includes computer programs, libraries and related non-executable data, such as online documentation or digital media. Computer hardware and software require each other and neither can be realistically used on its own.”

Components of computer hardware

1. Input/output
2. System unit
3. Processing unit
4. Storage devices

• Input devices are hardware devices which take information from the user of the computer system, convert it into electrical signals and transmit it to the processor. The primary function of input devices is to allow humans to interact with the computer system. For instance a mouse allows the user to control the movement of the pointer (a common element in user interface design).
• Output devices take data from the computer system and convert it to a form that can be interpreted by humans. For instance a monitor creates a visual electronic display to output information created by the processor to the user.
• System Unit is a box-like case that contains the electronic circuits that cause the processing of data to occur. Part of the computer system where the computing is done.  This is where the computer programs are executed and the data is manipulated.  It consists of the Central Processing Unit (CPU), memory (Random Access Memory-RAM), and other electronics.
• Processing devices are the components responsible for the processing of information within the computer system. This includes devices such as the CPU, memory and motherboard.
• Storage devices are components which allow data to be stored within a computer system. This includes devices such as hard disk drives and compact disk drives.

Basic input services

1. Keyboard
2. Mouse
3. Scanner
4. Touch pad

Output devices

1. Speaker
2. Monitor
3. Printer etc

Other parts of the computer (Software)

• Arithmetic/logic unit
  • Contains the electronic circuitry necessary to perform arithmetic and logical operations on data.
• Communications Devices
  • Enable a computer to connect to other computers. Devices that enable a computer to connect to other components; includes modems and network interface cards.
• Control Unit
  • The component in any computing system that works in coordination with the central processing unit to instruct, maintain and control the flow of information.
• Central Processing Unit (CPU)
  • The component in any computing system that represents the circuitry necessary to interpret and execute program instructions, it consists of the Control Unit, arithmetic/logic unit and the controller..  It is the corollary to the brain in organic systems.

ASSESSMENT

1. List 4 input devices
2. List 3 output devices
3. What is a computer hardware?
4. List 3 components of a computer hardware.

SS1 Computer Science First Term: Computer Output Devices

DEFINITION OF COMPUTER OUTPUT DEVICES

Computer Output Devices are various types of computer hardware which uses data and commands from the computer itself to perform assigned  tasks. In other words, the output devices facilitate data processing by carrying out commands given by the computer. They convert electronically-generated information into human-readable forms.

TYPES OF OUTPUT DEVICES: 

There are three types of output devices. These are discussed below-

Graphics Output (Visual): This is an output device that enables graphical contents to be displayed for viewing; usually on screen. These contents could be texts, images or moving pictures (videos). Please note that prior to being displayed on your computer screen, graphic files are stored on your computer, and they do not have physical size until they are displayed on screen or printed on paper. In this light therefore, graphics output devices are important for a wholesome use of the computer system.

 Tactile Output: These types of computer output devices are also used for displaying objects but mainly in the form of printing. Tactile output devices are also described as “handheld devices that use an array of vibrating pins to present a tactile outline of the characters or text under the viewing window of the device.”

Audio Output: These include everything from speakers to headphones and every audio-related devices that are used for the purpose of interpreting information from the computer system; albeit in an audio format. These information could include audio-texts, music and other sounds. 

EXAMPLES OF OUTPUT DEVICES:

1. Computer  Screens/Monitors
2. Digital Projectors
3. Printer
4. Speakers/Headphones
5. GPS
6. Braille Reader etc

ASSESSMENT.

1. Define computer output devices.
2. List and explain the types of output devices.
3. List the examples of output devices.
4. List and explain the types of printers.

OUTPUT DEVICES (PRINTER): SS1 FIRST TERM COMPUTER SCIENCE

WHAT IS A PRINTER?

A printer can be defined as an external output device that facilitates the production of electronic data into hard copy formats. In other words, a printer  will enable you to generate a physical (hard copy) file of your document. In various offices and schools, people print several copies of their work reports and assignments using the computer. Indeed, printers are important computer output devices used for printing several types of documents; mainly texts and pictures.  There are also various types and variants of printers as you shall see shortly.

TYPES OF PRINTERS

In computer science, we have two major types of printers. These are Impact and Non-impact printers. These types of printers shall now be separately defined and discussed below-

Impact Printer: Impact is a process of printing by which a printer works by banging a needle against an ink ribbon and making marks on the paper in the process. In other words, this type of printers work by hammering strikes against the paper through an ink ribbon. Though its printing quality is fairly good, impact printing has its demerits, chief among which is its excessive noise-making due to the constant banging of needles against the ink ribbons. Examples of Impact Printers are daisy-wheel printers, dot-matrix printers and line printers. These types of printers sharply contrast with laser and ink-jet printers which shall be discussed shortly under Non-impact printers.

Non-Impact Printer: These are printers which do not have to strike against a ribbon before texts or images can be printed on papers. Examples of such include  laser printers, ink-jet printer, LED page printer. In this vein, non-impact printers are very much unlike printers like the dot-matrix printer which (although the printing quality is good) makes a lot of noise due to the constant hammering. Most people currently use the non-impact printing system because it is noiseless while producing good quality prints. Above all, it is very fast too.

EXAMPLES OF PRINTERS

• 3D Printer: A 3D printer can create physical objects from a digital model of such objects by using materials such as metal alloys, polymers, or plastics. It was created Created in the year 1984 by a scientist called Charles Hull.

Other examples of printers include the following:

• All-in-one (AIO) printer
• Dot matrix printer
• Inkjet printer
• Laser printer
• LED printer
• Multifunction printer (MFP)
• Plotter
• Thermal printer

ASSESSMENT.

1. Define computer output devices.
2. List and explain the types of output devices.
3. List the examples of output devices.
4. List and explain the types of printers.