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Language design

Basic elements

Any Assembly language consists of 3 types of instruction statements which are used to define the program operations:

• opcode mnemonics
• data sections
• assembly directives

Opcode mnemonics

Instructions (statements) in assembly language are generally very simple, unlike those in high-level languages. Generally, an opcode is a symbolic name for a single executable machine language instruction, and there is at least one opcode mnemonic defined for each machine language instruction. Each instruction typically consists of an operation or opcode plus zero or more operands. Most instructions refer to a single value, or a pair of values. Operands can be either immediate (typically one byte values, coded in the instruction itself) or the addresses of data located elsewhere in storage. This is determined by the underlying processor architecture: the assembler merely reflects how this architecture works.

 Data sections

There are instructions used to define data elements to hold data and variables. They define what type of data, length and alignment of data. These instructions can also define whether the data is available to outside programs (programs assembled separately) or only to the program in which the data section is defined.

edit @ 7 Nov 2009 16:47:29 by doicpe