BASIC Programming Language for SS1
BASIC Programming Language for SS1
BASIC stands for Beginners All-purposed Symbolic Instruction Code. It was developed in 1964 by Professor John Kemeny and Thomas Kurtz to teach students at Dartmouth College. It has undergone series of historical development, which has resulted in several forms of the language.
Versions of BASIC
1. BASICA
2. GWBASIC
3. Torbo BASIC
4. Quick BASIC
5. VB.NET
BASIC CHARACTER SET
1. Alphabetic Characters – A to Z
2. Numeric Character – 0 to 9
3. Special Characters – 0 + % ^ # = ( ) etc
BASIC VARIABLES
A variable is a quantity that changes during the execution of a program. It can also be defined as a name that is used to represent some storage location.
Types of Variable
1. Numeric Variables : These are used to store numeric values such as 23, 98, etc. There are two major types of numeric variables, which are; Integer variable and real variable
a. Integers are whole numbers without decimal places.
b. Real numbers are numbers with decimal places
Hence Integer variable are names which the computer can assign integer values or constants to and real variable are name which the computer can assign real numbers or constant to. Integer variable name are written with a “%” sign as the last character. E.g. . When a numeric variable name is written without the % sign, it can take both integer and real numbers.
2. String Variables : These are used to store alphabetic and alpha-numeric values. A string variable name is always written with a dollar sign ($) as the last character. E.g. Name$=”John”
Rules for coding variable
1. In BASIC combining alphabets, numbers and decimal point (a maximum length of 40 characters) may for variable.
2. No reserve word can be used as a variable name.
3. Special characters cannot be used for naming variable.
4. A string variable corresponds to string data whereas a numeric variable corresponds to numeric data,
5. In a program, each variable is referred throughout the program by its name.
CONSTANTS
A constant is data that remains the same as the program runs (executes).
BASIC allows two types of constants:
1. Numeric constant: Numeric constant in BASIC is any signed or unsigned number.
2. Alpha-Numeric or string constant: It consists of the combination of letters, digits, and other symbols that is treated in a manner completely analogous to numeric constant. They are enclosed within inverted comma.
Rules for numeric constants
1. A number can have maximum of 8 digits
2. No comma is allowed
3. A decimal point can appear anywhere
4. If the value is quite larger it is expressed in exponent form
5. No blank space, special characters or any other letter is allowed in the number.
Expressions and Operators
In programming, an expression can be defined as the combination of operand and operator which is to be evaluated to produce answer. Operands are the data items involved in an expression. Operators determine the action to be carried out on the operand in the expression. For instance in the statement: LET C = A + B, A and B are the operands while “+” is the operator.
There are three major types of expression in BASIC. They are:
i. Arithmetic expression
ii. Relational Expression
iii. Logical expression
Arithmetic Expression and Arithmetical Operator
BASIC arithmetic expression is used to represent mathematical formulae in BASIC programming. Below is a list of BASIC arithmetic operators:
Arithmetic Operator
SYMBOL NAME FUNCTION
^ Upper caret Exponential
/ Slash Division
* Asterisk Multiplication
+ Plus Addition
- Minus Subtraction
Arithmetic Expression
Mathematical formulae BASIC Expression
lbc L*B*C
ut+1/2at^2 U*T+1/2*A*T^2
2(lb + bh + lh) 2*(L*b+B*H+L*H)
PTR/100 P*T*R/100
Relational Expression
Relational Expression is used for comparison of two or more data items. BASIC relational operators are listed below:
SYMBOL NAME
< Less than
> Greater than
= Equal to
<> Not equal to
<= Less than or equal to
>= Greater than or equal to
Logical Expression
Logical expression involve is an expression involving two or more relational repression joined by logical expression. BASIC logical operators are:
i. AND
ii. NOT
iii. OR
EVALUATION OF ARITHMETIC EXPRESSION
To evaluate arithmetic expression, the following order is followed:
PRIORITY OPERATOR
1st Parenthesis I.e. ( and )
2nd. Exponentiation
3rd. Multiplication and Division
4th Mod and Inter Division
5th Addition and Subtraction
Example: evaluate 4*A*B^2+ (A^2*B+C)/(A+B) if A=2; B=4 and c=2
Solution
Step 1 Substituting we have
4*2*4^2+ (2^2*4+2)/ (2+4)
Step 2 evaluate terms in the parenthesis
4*2*4^2+18/6
Step 3 evaluate 4^2
4*2*16+18/6
Step 4 evaluate 4*2*18 128+18/6
Step 5 evaluate 18/6 128 + 3
Step 6 evaluate 131
BASIC STATEMENT
1. LET Statement
The let statement is used to assign a numeric or string value to a variable.
Syntax
LET [variable] = [constant] for numeric value
LET [variable]$ = [“value”] for string value
Example
LET X = 12
LET B$ = “Clementina”
LET AREA = L*B
2. INPUT Statement
The INPUT statement is uses to enter data into the computer with a user prompt or a group of variable during program execution.
Syntax for numeric value
INPUT “[prompt]”; [variable]
Syntax for string value
INPUT “[prompt]”; [variable$]
Example
INPUT “type in the number”; A
INPUT “Type in your name”; N$
3. READ-DATA statement
READ and Data are two statement concerned with each other which are used to put data in a line of the program and to read the data when it is needed.
Example
READ A, B, C
DATA 5, 6, 7
LET SUM = A+B+C
PRINT SUM
END
4. REM (Remark) Statement
The REM statement is used to insert comments or remarks into a BASIC program. The use of remark statements improves the readability of the program. REM is a non-executable statement.
Syntax
REM [remark]
Example
REM program to add six numbers
5. PRINT statement
This statement is used to transmit data from the computer memory to the output device.
Examples
PRINT A
PRINT “I Like Writing Program”
Program Terminators (END and STOP)
6. STOP and END statement
The STOP statement is used to terminate the execution of a program at any point in the program. The END statement indicates the actual end of a program. The STOP statement may appear many times and anywhere, whereas an END statement can only appear at the end of a program and only once.
Example
REM END statement
PRINT “Good morning”
END
7. FOR – NEXT
Looping is used to have the computer do repetitive tasks in a fraction of the time that would be otherwise be required. The most common type of loop used in QBASIC programming is the FOR...NEXT and WHILE WEND loop that repeats a series of instructions a specified number of times.
Syntax
FOR variable=x TO y [STEP z]
.
.
.
NEXT [variable][,variable...]
x,y, and z are numeric expressions.
STEP z specifies the counter increment for each loop.
Example 1
FOR I = 1 TO 5
PRINT “the dullest pencil is better than the sharpest memory”
NEXT I
END
EXAMPLE 2
REM program to print odd numbers from 1 to 20
PRINT “odd numbers from 1 to 20 are”
FOR ODD =1 TO 20 STEP 2
PRINT ODD
NEXT ODD
END
SIMPLE BASIC PROGRAMS
Example 1: Program to find the sum and difference two number
10 REM this program accepts two numbers and finds their sum and difference
20 INPUT “Type the first number and press ENTER”; NUM1
30 INPUT “Type the second number and press ENTER”; NUM2
40 LET SUM = NUM1 + NUM2
50 LET DIFF = NUM1 – NUM2
60 PRINT “first number is “; NUM1
70 PRINT “second number is “; NUM2
80 PRINT “================”
90 PRINT NUM1; “+”; NUM1 “=” ; SUM
100 PRINT NUM1; “-“ ; NUM2 “=” DIFF
110 END
Example 2: program to calculate the area and perimeter of a rectangle
10 REM program to find the area and perimeter of a rectangle
20 INPUT “Type the length of the rectangle”; L
30 INPUT “Type the in the breadth of the rectangle”; B
40 LET AREA = L*B
50 LET PERI = 2 * (L + B)
60 PRINT “The area of the rectangle is “ ; AREA
70 PRINT “The perimeter of the rectangle is” ; PERI
80 END
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