Programming Language and Basic Language – JSS2 Computer Studies Lesson Note (Second Term)

A programming language is a set of words and grammatical rules used to instruct a computer to perform specific tasks.

Behavioural objectives

By the end of the lesson, students should be able to:

1. define a programming language and give examples;
2. distinguish between machine language, low-level language and high-level language;
3. list the elements required to construct a BASIC program;
4. use the QBasic math operators and the order of operation;
5. store the results of calculations in variables;
6. print the result of the calculations.

What is a programming language?

A programming language is a vocabulary and a set of grammatical rules for instructing a computer to perform specific tasks.

• Keywords: the words a language understands, such as PRINT and INPUT in BASIC.
• Syntax: the special rules for writing and organising program instructions.
• Program: a set of instructions written in a programming language.
• Programmer: the person who writes the program.

What are examples of programming languages?

• BASIC: a simple language for beginners. The name means Beginner’s All-purpose Symbolic Instruction Code.
• C and C++: general-purpose high-level languages.
• COBOL: used mainly for business data processing.
• FORTRAN: used mainly for science and engineering calculations.
• Pascal: often used to teach programming.
• Ada: a high-level language used in many technical systems.

What are the types of programming language?

There are three types of programming language: machine language, low-level language and high-level language.

What is machine language?

Machine language is a programming language that a computer can directly understand and obey without translation.

• Binary form: it is made up of only two characters, 0 and 1.
• Machine dependent: each type of CPU has its own machine language.
• Hard for people: it is difficult for humans to read and understand.

What is a low-level language?

A low-level language is a programming language whose commands map closely to the instructions of the computer’s processor.

• Little abstraction: it provides little or no distance from the computer’s instruction set.
• Examples: machine code and assembly language.
• Assembly language: uses short code words instead of 0s and 1s, so it needs translation into machine code.

What is a high-level language?

A high-level language is a programming language that is close to human language and far from machine language.

• Machine independent: programs are more or less independent of a particular type of computer.
• Easy to read and write: the words are close to English.
• Needs translation: a compiler or an interpreter converts it to machine language.
• Examples: BASIC, C, FORTRAN and Pascal.

What is the difference between the three types of language?

What are the elements of QBasic?

The elements required to construct a BASIC program are the character set, keywords, constants, variables, operators and expressions.

1. What is the character set?

The character set is the group of symbols that BASIC recognises.

• Alphabets: small and capital letters.
• Numbers: the digits 0 to 9.
• Special characters: symbols such as + – * / ( ) and $, each with its own meaning and function.

2. What are keywords?

Keywords are words that have special meanings in BASIC.

• Kinds: statements, reserved words, commands and names of operators.
• CLS: clears the screen.
• REM: adds a remark that the computer ignores.
• INPUT: collects data typed by the user.
• LET: gives a value to a variable.
• PRINT: displays output on the screen.
• Others: FOR, DO, SELECT, MID$, ASC, SQR, LEN, LEFT$, TIME$ and INT.

3. What are constants?

Constants are data or values in a program that cannot be changed during program execution.

1. String constant: letters, words or symbols in quotation marks, such as “LAGOS”.
2. Numeric constant: a number, such as 25 or 3.5.

4. What are variables?

A variable is a named place that stores data needed in a program.

1. String variable: stores text. Its name ends with $, as in NAME$.
2. Numeric variable: stores numbers, as in A or TOTAL.

• Naming rule: a variable name starts with a letter and must not be a keyword.
• Value: the stored value can change while the program runs.

5. What are operators?

Operators are symbols that tell BASIC the type of operation to perform on data.

• Arithmetic operators: do calculations, such as + and *.
• Relational operators: compare values, such as =, <, > and <>.
• Logical operators: combine conditions, such as AND, OR and NOT.
• String operators: join text, using the + sign.

6. What are expressions?

An expression is a combination of constants, variables and operators that gives a value.

• Example: A + B * 2 is an expression.

What are the QBasic math operators?

A math operator is a symbol used for addition, subtraction, multiplication, division or other calculations.

What is integer division?

Integer division (\) divides one number by another and gives only the whole-number part of the answer.

• Ordinary division: 95 / 2 gives 47.5.
• Integer division: 95 \ 2 gives 47, with no decimal part.
• Decimal numbers: QBasic rounds each number to a whole number before dividing.

What is the order of operation in QBasic?

The order of operation is the sequence in which QBasic works out the operators in an expression.

• 2 + 3 * 4: multiplication first, so the answer is 14.
• (2 + 3) * 4: brackets first, so the answer is 20.
• 20 / 4 + 2: division first, so the answer is 7.

How do you store and print the result of a calculation?

You store a result by assigning it to a variable with LET, then display it with PRINT.

1. Type CLS to clear the screen.
2. Give values to variables using LET.
3. Write an expression and store its result in a new variable.
4. Use PRINT to display the variable.
5. Press F5 to run the program.

Evaluation

1. What is a programming language?
2. Give three examples of programming languages.
3. What is machine language?
4. Name the four types of operators in BASIC.
5. What is the result of 95\2 in QBasic?

Assignment

1. List the elements required to construct a BASIC program, then write the seven QBasic math operators with their meanings.