Introduction to computers and programming  (Page 2/5)

Another term for a program or a set of programs is software , and we use both terms interchangeably throughout the text.

Writing computer programs is called computer programming .

The languages used to create computer programs are called programming languages .

To understand C++ programming, it is helpful to know a little background about how current programming languages evolved.

Machine and assembly languages

Machine languages are the lowest level of computer languages. Programs written in machine language consist of entirely of 1s and 0s.

Programs in machine language can control directly to the computer’s hardware.

00101010 000000000001 000000000010

10011001 000000000010 000000000011

A machine language instruction consists of two parts: an instruction part and an address part.

The instruction part (opcode) is the leftmost group of bits in the instruction and tells the computer the operation to be performed.

The address part specifies the memory address of the data to be used in the instruction.

Assembly languages perform the same tasks as machine languages, but use symbolic names for opcodes and operands instead of 1s and 0s.

LOAD BASEPAY

ADD OVERPAY

STORE GROSSPAY

Since computers can only execute machine language programs, an assembly language program must be translated into a machine language program before it can be executed on a computer.

Machine languages and assembly languages are called low-level languages since they are closest to computer hardware.

High-level programming languages

High-level programming languages create computer programs using instructions that much easier to understand than machine or assembly language instructions.

Programs written in a high-level language must be translated into a low level language using a program called a compiler .

A compiler translates programming code into a low-level format.

High-level languages allow programmers to write instructions that look like every English sentences and commonly used mathematical notations.

Each line in a high-level language program is called a statement .

Ex: Result = (First + Second)*Third.

Once a program is written in a high-level language, it must also be translated into the machine language of the computer on which it will be run. This translation can be accomplished in two ways.

When each statement in a high-level source program is translated individually and executed immediately upon translation, the programming language used is called an interpreted language , and the program doing the translation is called an interpreter .

When all of the statements in a high-level source program are translated as a complete unit before any one statement is executed, the programming language used is called is called a compiled language . In this case, the program doing the translation is called a compiler .

Application and system software

Two types of computer programs are: application software and system software.

Application software consists of those programs written to perform particular tasks required by the users.