Computer Science - Assembly and Machine Code This presentation explains the 2 types of programming languages such as assembly and machine code.

1. Computer Science
(A Level)
Assembly and
Machine Code

2. A way of programming that involves
writing mnemonics
(Definitions)
Short codes that are used as instructions
when programming

3. • Rather than using sequences of 0s and 1s, an assembly language allows
programmers to write code using words.
• Assembly language can be seen as machine code with words
• Assembly code generally used a small number of words/letters per word.
• The commands translate directly into one command in machine code
(this is called one-to-one relationship)
• Most assembly code (not all), use abbreviated words called mnemonics
(e.g. LDR  Load, STR  Store, SUB  Subtract)
• Before assembly code (source code)can be executed it has to be
converted into machine code (object code), this is because the processer
can only understand binary. This conversion happens through an
assembler
Assembly Language

4. Assembly Language
Advantages Disadvantages
• Easier to understand and therefore, saves
a lot of time and effort of the
programmer
• Machine dependent
• It is easier to correct errors and modify
program instructions
• You must directly control the exact
instruction sequences the processor
executes
• Assembly Language has the same
efficiency of execution as the machine
level language because this is one-to-
one translator
• Code is relatively compact
• Allows direct manipulation if registers on
the processor

5. Lowest level of code made up of
0s and 1s (binary)
(Definitions)

6. • The processor of a computer can only understand
binary digits (0s and 1s), therefore all instructions
given to the computer should be written in binary
also known as Machine Code.
• In machine code, a typical instruction holds an
operation code (opcode) in first 4 bits and the
operand (the data to be operated on or the address
where the data is held) in the second 4 bits
Machine Code

7. Machine Code
Advantages Disadvantages
• It can run very fast because no
translation program is required for
the CPU
• Difficult to track down errors or bugs
• Unlikely to be portable as it is writer for a specific
processor and therefore can only work on a
computer with the same type processor.
• It is very difficult to program in machine
language. The programmer has to know details
of hardware to write program
• The programmer has to remember a lot of codes
to write a program which results in program
errors