QBasic
- QBasic is a high level programming language developed by Microsoft Corporation in 1985. It is modular programming language where program is divided in different modules or procedures. Qbasic is easy to learn. It uses English like keywords and mathematical symbols to write a program.
- Elements of QBASIC programming
To construct the QBASIC program, we have to arrange some standard elements.The elements used in Qbasic are as follows: Character set Variables Constants Operator and Operands Expression StatementsCharacter Set:QBASIC has the character set consisting of the following elements: Alphabets: A, B, C,....Z Digits: 0, 1, 2........,9 and Special characters: + - * / ( ) . , $ ; ,: ,= ,> ,< , ^
The symbol ^ (caret) is used to denote exponentiation operator, the symbol * (asterisk) is used to denote multiplication and other symbols; have their usual meanings.
ConstantsA quantity in a computer program which does not change its value during the execution of the program is called a constant. QBASIC allows the following constants:.Numeric constantThe numeric constant is one that is formed by a sequence of digits 0, 1, 2,.....9 and may include a decimal point. A numeric constant may be an integer or a real number. 383, +57, 0, -6.2 and 6.15E4 are valid numeric constants. The number 6.15E4, in fact, represent 6.15 * 104. The notation E is used to represent the exponential form. The number after E is the exponent which can be positive or negative. However, its length cannot exceed two digits.It is also important to keep in mind that:QBASIC does not distinguish between an integer and fraction. Commands are not allowed in a numeric constant. The limit on the number of digits that can be used varies from computer to computer.Normally, a numeric constant can have up to a maximum of eight digits.String constantA string constant consists of a sequence of characters which must be enclosed by a quotation mark.Variableshe quantity which may change its values during the execution of the program is called the variable.In QBASIC, variables are also of two types:1.Numeric variable: Numeric variable can assume numeric value and is represented by an alphabet or an alphabet followed by another alphabet or digit. For example A, C, A2, ABC, A6 etc, represent numeric variables.2.String variable: A string variable is represented by an alphabet followed by dollar ($)sign.Itshouldbekeptinmindthatwhileconstructingthestringvariable,dollar($) should be the last character. For example, B1,NAME , BOOK1$, etc are valid string variables.ExpressionAn expression can be a string, or numeric constant, a variable or a combination of constants, variables with operators which returns a single value.
OperandsOperands are the data or variables on which mathematical, logical and string operations take place.OperatorsOperators are the symbols, which are used in arithmetic operations, logical expressions, and string expressions.Statements A statement is a set of instructions written using keywords or commands of QBASIC. Every programming language uses keywords as a statement with certain syntax.
- Elements of QBASIC programming
To construct the QBASIC program, we have to arrange some standard elements.The elements used in Qbasic are as follows:
Character set
Variables Constants
Operator and Operands
Expression
Statements
Character Set:
QBASIC has the character set consisting of the following elements:
Alphabets: A, B, C,....Z
Digits: 0, 1, 2........,9 and
Special characters: + - * / ( ) . , $ ; ,: ,= ,> ,< , ^
The symbol ^ (caret) is used to denote exponentiation operator, the symbol * (asterisk) is used to denote multiplication and other symbols; have their usual meanings.
Constants
A quantity in a computer program which does not change its value during the execution of the program is called a constant. QBASIC allows the following constants:
.Numeric constant
The numeric constant is one that is formed by a sequence of digits 0, 1, 2,.....9 and may include a decimal point. A numeric constant may be an integer or a real number. 383, +57, 0, -6.2 and 6.15E4 are valid numeric constants. The number 6.15E4, in fact, represent 6.15 * 104. The notation E is used to represent the exponential form. The number after E is the exponent which can be positive or negative. However, its length cannot exceed two digits.
It is also important to keep in mind that:
QBASIC does not distinguish between an integer and fraction. Commands are not allowed in a numeric constant.
The limit on the number of digits that can be used varies from computer to computer.
Normally, a numeric constant can have up to a maximum of eight digits.
String constant
A string constant consists of a sequence of characters which must be enclosed by a quotation mark.
Variables
he quantity which may change its values during the execution of the program is called the variable.
In QBASIC, variables are also of two types:
1.Numeric variable: Numeric variable can assume numeric value and is represented by an alphabet or an alphabet followed by another alphabet or digit. For example A, C, A2, ABC, A6 etc, represent numeric variables.
2.String variable: A string variable is represented by an alphabet followed by dollar ($)sign.Itshouldbekeptinmindthatwhileconstructingthestringvariable,dollar($) should be the last character. For example, B1,NAME , BOOK1$, etc are valid string variables.
Expression
An expression can be a string, or numeric constant, a variable or a combination of constants, variables with operators which returns a single value.
Operands
Operands are the data or variables on which mathematical, logical and string operations take place.
Operators
Operators are the symbols, which are used in arithmetic operations, logical expressions, and string expressions.
Statements
A statement is a set of instructions written using keywords or commands of QBASIC. Every programming language uses keywords as a statement with certain syntax.
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