CBSE Class 6 Computer Science Computer Languages Notes Set 02

Why a computer needs a language

People use language to share ideas. In the same way, we need a language to give instructions to a computer. A computer cannot think for itself and works only step by step. A set of instructions given to a computer to do a task is called a program, and the work of writing a program is called programming. Every programming language has its own rules for writing statements, and these rules are called its syntax.

Types of computer languages

Computer languages are grouped into generations according to how close they are to the machine and how easy they are for people to use.

1. Machine language (first generation)

This is the only language that a computer can understand directly. It is written using just two digits, 0 and 1 (binary code), where 0 stands for the OFF state and 1 for the ON state. Programs in machine language run very fast and use little memory. However, it is very hard for people to read, write and correct, and it depends on the machine, so a program written for one type of computer may not work on another. For this reason it is called a low-level language.

2. Assembly language (second generation)

Assembly language replaces strings of 0s and 1s with short codes called mnemonics, such as ADD for addition. It is easier to use than machine language, but the computer cannot understand it directly. A translator program called an assembler converts it into machine language. It is also a low-level, machine-dependent language.

3. High-level language (third generation)

High-level languages use English-like words and mathematical symbols, which makes them easy to learn and use. They are machine independent, so the same program can run on different computers with small changes. Examples are C, Java and Python. Since the computer understands only machine language, a high-level program must be translated by one of two translators:

1. Interpreter: translates and runs the program one line at a time. If there is an error, it stops at that line, so mistakes are easy to find. It is slower and is good for beginners.

2. Compiler: translates the whole program into machine language in one go and then runs it. It is faster than an interpreter, but it reports errors only after reading the whole program.

4. Fourth generation languages (4GL)

These are more advanced and closer to human language. They are very user friendly, do not depend on a particular operating system, run fast, and let the user get the required result with little effort. They are designed to cut the time and cost of making software. Languages used to work with databases, such as SQL, are examples.

Source program and object program

A program written in assembly or a high-level language is the source program. When a translator converts it into machine language, the result is called the object program.

Comparison at a glance

1. Machine language: 0s and 1s, fastest, hardest to use, no translator needed.

2. Assembly language: mnemonics, needs an assembler.

3. High-level language: English-like, needs an interpreter or compiler.

4. 4GL: nearest to human language, easiest for the user.

Worked examples

Example 1. A programmer wrote a program using the code ADD and MOV. Which language is this and what is needed to run it? Solution: Short codes such as ADD and MOV are mnemonics, so this is assembly language. It must first be converted into machine language by an assembler.

Example 2. A beginner wants to find mistakes in a program easily. Should she use an interpreter or a compiler? Solution: An interpreter, because it executes the program line by line and stops at the first error, which shows exactly where the mistake is.

Example 3. Why can a high-level program written on one computer usually run on another, but a machine language program may not? Solution: High-level languages are machine independent and are translated for each machine, whereas machine language depends on the design of a particular computer.

Quick Check Questions