Page 18 - DCAP102_DCAP_401_Foundations of Computer Programming

Unit 1: Foundation of Programming Languages

Some other examples of using these directives are: Notes

TEMP DB 0111001B ; Binary value in byte operand
; named temp
VALI DW 7341Q ; Octal value assigned to word
; variable
Decimal DB 49 ; Decimal value 49 contained in
; byte variable

HEX DW 03B2AH ; Hex decimal value in word
; operand
ASCII DB ‘EXAMPLE’ ; ASCII array of values.

1.6 Machine Level Language

Although computers can be programmed to understand many different computer languages,
there is only one language understood by the computer without using a translation program,
this language is called the machine language or the machine code of the computer. Machine code
is the fundamental language of a computer and is normally written as strings of binary 1s and
0s. the circuitry of a computer is wired in such a way that it immediately recognizes the machine
language and converts it into the electrical signals needed to run the computer.
An instruction prepared in any language has a two part format, as shown in Figure 1.1. The fi rst
part is command or operation, and it tells the computer what function to perform. Every computer
has an operation code or opcode for each of its functions. The second part of the instruction is the

operand, and it tells the computer where to find or store the data or other instructions that are to
be maintained. Thus, each instruction tells the control unit of the CPU what to do and the length
and location of the data field are involved in the operation. Typical operations involve reading,

adding, subtracting, writing and so on.
Figure 1.1: Instruction Format

OPCODE OPERAND
(operation code) (Address/Location)

We already know that all commuters use binary digits (0s and 1s) for performing operations.
Hence, most computers machine language consists of strings of binary numbers and is the only
one the CPU directly understands. When stored inside the computer, the symbols which make
up the machine language program are made up of 1s and 0s.

Example: A typical program instruction to print out a number on the printer might be.

101100111111010011101100110000111001
The program to add two numbers in memory and print the result look something like the
following:
001000000000001100111001

001111000000111111000111

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