COMPUTER STUDIES SS1 (SECOND TERM 2016/17 SESSION)

SCHEME OF WORK

1. Output devices
2. Computer System software
3. Computer Application software
4. Programming Languages
5. BASIC programming language

TOPIC ONE: OUTPUT DEVICES

Output devices are devices that enable the computer to communicate the results of data processing carried out by it to the user. These devices enable the computer to display text, graphics (pictures and images) and produce sound. Examples of computer output devices include monitor, printer, speaker, plotter, braille embosser etc.

Features and uses of output devices

1. Monitor: The monitor, also called Visual Display Unit (VDU) is a TV-like structure attached to the System Unit through the VGA cable. It displays text and graphics (pictures and images). The content showing on the monitor is called a soft copy.

2. Printer: A printer is a device attached to the System Unit through the USB cable or other types of cable. It is used to produce the information (text, graphics, images, illustrations) showing on the monitor on paper, transparencies, and plastic. Such a printout is called a hardcopy.

3. Speaker: A speaker is a device used for producing sound captured by the microphone or music in mp3, wav, etc. formats. Speakers come in different forms such as headphones, earphone, canalphones, headset etc. and can also be used with portable devices such as mp3 player, mobile phones etc.

4. Plotter: A special type of printer used for printing drawings, charts, maps etc. using multi-coloured automated pens. It is usually used by architects, engineers and surveyors. They are rarely used now and are being replaced by wide-format conventional printers, which can produce high-quality graphics.

5. Projector:  A device that helps direct the content on a display screen (monitor) onto a particular flat surface.

6. Braille Embosser

Structure and type of CRT monitor

The Cathode Ray Tube (CRT) used as a computer monitor was invented by Karl Ferdinand Braun. This monitor employs the CRT technology used most commonly in the manufacturing of television screens. In this, a stream of intense high energy electron is used to form images on a fluorescent screen. A cathode ray tube is basically a vacuum tube containing an electron gun at one end and a fluorescent screen at another end. From this electron gun, a process called thermionic emission generates a strong beam of electrons. These electrons travel through a narrow path within the tube with high speed using various electro-magnetic devices and finally strike the phosphor points present on the fluorescent screen, thus creating an image.

Today, CRT monitor are being replaced with flat Plasma screen, Liquid Crystal Display (LCD).

CRT monitor

Types of monitor

There are two types of monitor, namely:

1. Monochrome monitor: This monitor displays its characters in only one colour. The colour could be white, green or amber. Looking at the monochrome monitor, one can see two colours; one colour for the background and one for the foreground. The two colour combinations can therefore be black and white, green and black or amber and black.

2. Colour monitor: This monitor displays information in colours. It is similar to a colour television but it handles data more quickly and has a sharper output.

Types of printer

There are two types of printer, namely impact and non-impact printers.

I. IMPACT PRINTERS: This type of printer behaves like a typewriter whereby a character is printed when a metal slug strikes on a carbon ribbon. Impact printers have contact with the surface of the paper. Examples of impact printer include the following:

A. DOT MATRIX printer: This prints characters and graphic images by impacting a ribbon and transferring dots of ink onto the paper. It prints dot matrix characters by pressing the end of selected wires against ribbon and paper. The dots are used to form the characters and images on the paper.

B. LINE printer: This prints a line of characters at a time. The output speed is between 200 to 3000 lines per minute (LPM)

C. CHARACTER printer: This prints one character at a time moving across the paper. The output speed range from 200 to 400 characters per second (cps)

II. NON-IMPACT PRINTER

Non-impact printer creates images on paper in a manner similar to that of a photocopying machine. They do not have contact with the surface of the paper. Examples include:

A. INK JET printer: This prints by spraying small streams of quick-drying ink onto the paper and using it to form characters, shapes and images. The ink is stored in disposable ink cartridges, which can be black or coloured. They are found in homes and offices.

B. LASER printer: This uses an electrically charged drum to transfer toner or dry ink onto paper like the photocopier does. It traces an image by using a computer-controlled laser beam.

C. THERMAL printer: This prints by transferring dots of ink or dye from a ribbon onto paper and passing the ribbon and the paper across a line of heating elements. The characters are produced with a print head containing a matrix of small heating elements. This printer is very quiet in operation because the printer head does not strike the paper.

DIFFERENCES BETWEEN IMPACT AND NON-IMPACT PRINTER

IMPACT PRINTER	NON-IMPACT PRINTER
Makes noise while printing	Does not make noise while printing
Produces low quality images	Produces high quality images
Uses ribbon to print	Uses ink (dry and wet) to print
Does not have heating element	Has heating element that dries the ink on paper
Prints only one colour at a time	Can print more than one colour at a time
Has striking pins/heads that strike the characters or dots on paper	Does not have striking pin heads to strike characters on paper

DIFFERENCES BETWEEN THE MONITOR AND THE PRINTER

MONITOR	PRINTER
Has screen	Has no screen
Uses no ribbon, ink, cartridge or toner	Uses ribbon, cartridge,  ink or toner
Uses no paper	Uses paper and printable medium
Display texts, images and pictures	Prints text, images and pictures on paper
Some have vacuum tubes or a liquid crystal	Has no vacuum tube or a liquid crystal
Has no paper tray	Some have paper tray

TOPIC 2: COMPUTER SYSTEM SOFTWARE

Definition of software

A computer software (or software) is a general term used to describe a set of instructions usually called a program, which control the operation of a computer or used to accomplish a specific task.

Types of software

Software can be broadly divided into two, namely:

i. System software: This software helps direct and control the running of computer’s hardware and other connected devices. It helps to manage computer resources such as memory and processor. Examples include Operating system, Translators and utility software.

ii. Application software: This software enables the computer to perform specific tasks. Examples include word processing package, spreadsheet package, game software etc.

Types of System software

1. Operating system: Operating system is a suite/set (collection) of programs/software that controls the execution of application programs and coordinates/manages the hardware components. It can also be defined as a set of programs that controls and manages computer resources/components and provides other useful services. The purpose of an operating system is to provide an environment in which a user can execute programs in a convenient and efficient manner.

 Functions of Operating system

i.         Serves as an interface between the user and the computer/hardware and software

ii.        Access control/ System Security: By means of password and other similar access control techniques the OS prevents unauthorized access to programs and data.

iii.  Controls program execution: The OS runs and controls all other system programs and application software

iv.   Booting/Starting up the computer: The operating system manages the starting up of the computer

v.        Controls hardware resources

vi. File-system manipulation (for users and their programs) - read and write files and directories, create and delete them, search them, list file Information, permission management.

vii. Control over system performance:  The OS records the delay between the request for a service and the response from the system and manages the situation accordingly.

viii.  Protects the system from errors and failures/error handling

ix.  Task management: The OS gives control to the program the user brings to the foreground (from among multiple opened programs).

x.   Job management: The OS controls the order and time a particular operation is executed. Example is when multiple print commands is sent to the printer, the OS spools the content and schedule which one prints first in a First Come First Serve (FCFS) approach.

xi.  Device management: The device management function controls hardware devices by using special software called device drivers, which are installed in the operating system. This makes the operating system recognize the device.

xii. Resource allocation: When multiple users or multiple jobs running concurrently, the OS allocates and de-allocates resources (such as CPU cycle, main memory, I/O devices etc.) based on the availability of a particular resource and assign it to any user or program requesting for it.

xiii. Memory management

Examples of Operating system

Operating system can be grouped into two, namely, the Graphical User Interface (GUI) and the Command Line Interface (CLI).

·       The GUI group makes use of windows, icons, mouse, scroll bar, and Pointer. In this group, we have the Microsoft series (Windows 95, 98, NT/2000, ME, XP, Vista, 7, 8,10), Chrome OS, Apple System 7 and macOS, Linux variants like Ubuntu.

·     The CLI group includes the IBM Disk Operating system (DOS) that is phased out, the Microsoft Disk Operation System (MS-DOS) and UNIX. The Command line is a text-based interface that allows the user to interact with the computer system by typing in commands (instructions).

2. Translators: Translators are programs that convert programs written in languages other than the machine language to machine language. Examples are Assembler, Interpreter and compiler.

3. Utility Software: Utility software is system software designed to help analyze, configure, optimize or maintain the operation of a computer, its devices, or its software. Examples include disk utilities like defragmenters, compressors and cleaner. There are also other operating system utilities such as antivirus programs, registry cleaners, Screen saver, file viewer (windows explorer), editors and system restoration programs. Utility software are built into the computer operating system, however may be installed separately. 

TOPIC 3: COMPUTER APPLICATION SOFTWARE

Application software are the programs that enable computer to perform specific productive task.

Types of application software

1. User application development program: This kind of software is used to develop programs usually called in-house programs, which are customized to perform specific functions for the user such as administration, payroll, production control, banking, inventory etc. Examples include NetBeans, Eclipse etc.

2. Application packages: The application packages are software packages that perform generalized functions and are produced for the general public to use. This category of software can be grouped based on their functions as listed below:

1. Database management: Examples include Microsoft Access, Oracle, MySQL, Dbase etc. which are used for creating, maintaining and updating databases (collection of related information).
2. Word processing: Examples include Microsoft Word, Lotus WordPro, Corel WordPerfect, Professional Write etc. are used to create document such as letter, memos made up of textual and graphical information.
3. Spreadsheet, calculation and data analysis: Examples include Microsoft Excel, Amipro, Quattro Pro, Lotus 1-2-3 etc. which contains grids of cells arranged in rows and columns used for entering data for calculation and analysis.
4. Graphic designing: Examples include Corel Draw, Adobe Photoshop, Paint etc. which can be used to draw and make designs related to graphics.
5. Slide presentation: Examples include Microsoft PowerPoint, Impress, Prezi etc. which contains collection of slides used to hold information that can be presented in form of slide show.
6. Email management: Examples include Microsoft Outlook, MS Exchange etc. which contains tools for sending and receiving electronic mail (e-mail).

TOPIC 4: PROGRAMMING LANGUAGES

Computer programming is the specification of instructions that a computer follows to perform a particular task.

A computer program is a sequence of instructions that tells a computer what to do and how to do it.

A programming language is a language used to write instructions for the computer. Programming language, like any human language has rules and grammar that governs the formation of a statement.

The syntax of a language describes the possible combinations of symbols that form a correct statement. The meaning given to these combinations of symbols is called semantics.

Levels of programming

1. Machine language: Is a system of instructions and data directly understood by the computer’s central processing unit. These instructions and data are combinations of sequence of bits (0’s and 1’s) with different patterns corresponding to different commands to the machine.
2. Low level (Assembly) language: This language uses abbreviations or symbolic letter codes (mnemonics) to write each machine-language instruction. The letter codes are used in place of binary digits. Programs written in Assembly language are translated into machine language by an Assembler.
3. High level language: The instructions of this language are written using words that are very close to human languages and algebra-type expression. They are closer to human understanding and are translated into machine language by a compiler or an interpreter.

Features/characteristics of each level of programming language

i)                 Machine language

1.    These instructions consist of binary numbers (set of 0’s and 1’s)

2.  This language is machine dependent i.e. instructions written for a particular type of computer can only be executed on that particular computer(machine).

3.     It is very hard for people to write and understand thus making the programs error prone.

4.     Each CPU design has its own machine language, which is the set of instructions that the CPU of that machine understands and executes.

ii)                  Low level ( or Assembly) language

1.      Uses mnemonics (symbolic operation codes) and operands (symbolic storage address).

2.      Machine dependent

3.      For any assembly language instruction, one machine language instruction is generated.

4.      It illustrates fundamentals of computer construction and operation.

iii)             High level languages

1.    Machine independent: programs written or compiled on one type of Computer can be executed (run) on different type of computer that has different architecture.

2.      It uses instructions that seem English-like and thus closer to human understanding.

3.      Easy to detect errors

4.      Consists of well-defined syntax and standard.

5.     Requires a compiler to translate into machine language before the computer can execute them.

6.    Programs written in HLL are called source code and the compiled version is called object code.

Comparison of levels of Programming Languages

MACHINE LANGUAGE	ASSEMBLY LANGUAGE	HIGH LEVEL LANGUAGE
Difficult to learn, write and debug	It is difficult but easier than machine language	It is easier to learn, write and debug
It is machine dependent	Machine dependent	Machine independent
Does not require a translator	Requires a translator called Assembler	Requires a translator called a compiler or interpreter
Instructions consist of binary digits (1’s and 0’s)	Instructions consist of symbols and mnemonics	Instructions consist of English-like words, symbols and numeric.

Examples of Programming Language

The following are some of the many programming languages:

Ada, Algol, APL, BASIC, C, C++, C#, COBOL, FORTRAN, Java, JavaScript, LISP, Pascal, PHP, Perl, Python, Visual Basic etc.

TOPIC 5: BASIC Programming language

The BASIC programming language was developed in 1964 by John G. Kemeny and Thomas Kurtz at Dartmouth College. BASIC is an acronym that stands for “Beginner’s All-Purpose Symbolic Instruction Code”

Basic Character Set

A character set is simply a list of letters, numbers and symbols that provide one with the characters used in a particular language. BASIC as a language has its own character set, they include the following:

·         Alphabets characters (A to Z or a to z)

·         Numeric character (0, 1 to 9) including hexadecimal characters.

·         Special characters (such as $,#,!, ^ etc.) that perform special functions in BASIC

 Arithmetic operators

CHARACTER	NAME	USE
*	Asterisk	For multiplication, e.g. A*B or (3*5)
-	Minus	For subtraction, e.g. M-N or (4-1)
+	Plus	For addition, e.g. K+N or (1+6)
/	Forward slash	For real division, e.g. A/B or (7/3)=2.33
\	Bask slash	For integer division, e.g. P\G or (7\3)=2
^	Caret	For exponentiation, e.g. A^B or (7^3)

Relational (Comparison) Operator

CHARACTER	NAME	USE
=	Equal to	A=B
>	Greater than	A>B
<	Less than	A<B
> =	Greater than or Equal to	A >=B
< =	Less than or Equal to	A <= B

Data types

Data type is a description of the set of values and the basic set of operation that can be applied to values of the type.

i)                    Integers: a positive or negative number without decimal. It has a range of values from -32,768 to 32,767. Each value is stored using 2 bytes of memory (storage) space.

ii)                  Real numbers: numbers with fractional parts or with a decimal point. It is stored using 4 bytes of memory space.

iii)                Boolean: consist of only two values; “YES and NO” or “True or False” or 1 or 0.

iv)                String: a sequence of characters in double quote. For example, “Computer Studies” is a string value with 16 characters. Each character is stored using 8 bits (one byte) in the ASCII character set and two byte in the UNICODE character set. Alphabet is represented in ASCII.

Keyword

Keywords are words that have special meaning and function in BASIC. Such words must be used strictly according to their functions, otherwise the computer will respond with error message.

Here are some of the BASIC keywords and their uses

KEYWORDS	USE	EXAMPLE
REM	Make comment about an instruction or about the whole program	10 REM Program to add two numbers
INPUT	Used to ask the user to supply the data to be processed while the program is executing	5 INPUT A,B,C
PRINT	Used to display the output of operation on the screen	PRINT “The values”, A,B
LET	Used to assign a value to a variable	3 LET A=5
READ	Used to tell the computer that the data to be processed is supplied within the program statements. Used together with DATA keyword	10 READ A,B
DATA	Used to show the computer the data it is asked to read in the READ statement. Used along with READ keyword.	10 DATA 4,7
END	To end the program	5 END

Variables and Constant

A variable is an identifier or a name of a memory location where data (values) can be placed or stored. Because the value placed in a memory location can be changed at any time, we call such memory location “a variable”. However, when the value of a memory location is not to be changed, we refer to such memory location as “constant”.

Declaration of Variables and Constants

When you are to supply data to the computer for processing, you are required to state the data type. This help the computer to interpret it and an appropriate storage space is reserved for the data. To achieve this, the keyword DIMENSION (or DIM) is used to specify the data type. For example, variable Name and Pie are to hold “character and real” data values respectively. This can be written in BASIC as follows:

1.      DIM Char Name, INT Age, REAL Height

2.      DIM Name AS Char, Age AS INT, Height AS Real

3.      DIM Name$, Age%, Height!

Rules for naming Variable

1. Every variable must begin with an English alphabet (A to Z or a to z).
2. The name must not be more than 40 characters in length.
3. Names can be alphanumeric (combinations of alphabet and numbers
4. Name must not be any keyword
5. Do not include a blank space in the name.

 Basic Expression

A BASIC expression is formed when two or more characters, strings, variables or constants are combined with arithmetic, relational or logical operators

Examples include:

1.      F2 + 7 (add 7 to the value in the variable F2)

2.      A+ B (add the value in A to the value in B)

Arithmetic expression and their BASIC expression

Algebraic expression	BASIC expression
A ÷ B	A/B
2b2+5c	2*(b^2)+5*c
-b±√b2-4ac/(2a)	(-b+sqr(b^2 – 4*a*c))/2*a

Arithmetic operation precedence

The rule that guides the order in which operation must be performed in an expression is known as “precedence” rule.

THE ORDER	SYMBOL	NAME
1	( )	Bracket
2	^	Exponentiation
3	-	Negation
4	*or /	Multiplication
5	\	Integer
6	MOD	Modulo (remainder)
7	+ or -	Addition or subtraction

BASIC statements

A BASIC statement is any valid instruction given to the computer for processing of data. BASIC statement may be an expression, an assignment, a reserved word (keyword) with or without arguments or their logical combinations

1.      Declaration statement: Every variable in a program must be declared before it can be used. A variable must be declared with appropriate data type. Example of declaration statements are

a. DIM Age AS Integer

b. DIM Name AS Character

 2.      Assignment statement: This statement causes a computer to store a value in a variable. The statement has two sides separated by the equality sign (=).

 a. Name = “Computer Studies”

 b, Age = 16

 3.      INPUT statement: This statement is used to ask the user to supply the data to be processed while the program is executing.

 a. INPUT Name$, Age%       (This statement is not interactive)

b. INPUT “Enter the Name and Age”, Name, Age          (This statement is interactive)

 4.      READ and DATA statement: The READ statement is used to supply data into the program, but unlike the INPUT statement, the programmer supplies the data inside the program codes using the DATA keyword.

 a. READ “Enter Name and Age”, Name$, Age%

 b. DATA “Jide Babs”, 20

 5.      PRINT statement: This statement is used to show the result of data processed.

A simple QBASIC program

1    REM This program calculates the area of any rectangle and print the length, width, and area.

2    ‘To calculate the Area of a Rectangle we must know its length and width

3    Length = 10

4    Width = 6

5    Area = length * breadth

6    PRINT “Area is “, Area

7    END

Another program solving Quadratic equation is shown below.

1. REM program to solve a quadratic equation
2. INPUT “Enter coefficients a, b, c “; a,b,c
3. Discrim = b^2 – 4*a*c
4. If Discrim > 0 then
5. Dummy = sqr(Discrim)
6. PRINT “There are 2 distinct roots”
7. PRINT “first root (X1) = “; (-b + dummy)/(2*a)
8. PRINT “Second root (X2) = ”; (-b –dummy)/ (2*a)
9. ELSEIF Discrim = 0 THEN
10. PRINT “There is only 1 root, the 2 roots coincide”
11. PRINT “double root = ”;  - b / (2*a)
12. ELSE
13. PRINT “The roots are imaginary”
14. Dummy = sqr (- discrim)
15. PRINT “Real part = “; - b /(2*a)
16. PRINT “Imaginary part = ”; dummy/(2*a)
17. END IF
18. END