21CS208 / Operating Systems Unit - I
21CS208 – OPERATING SYSTEMS
UNIT I - OVERVIEW OF SYSTEM SOFTWARE
Assemblers & Macro Processors: Simple Assembly Scheme, Pass Structure of assemblers, Macro
Definition and Call, Macro Expansion, Nested Macro Calls, Linkers and Loaders: Introduction,
Relocation and linking Concepts and Types of Loaders.
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1.1 Assemblers:
System Software is a set of programs that manage the resources of a computer system. System
Software is a collection of system programs that perform a variety of functions.
Definition:
The Assembler is a Software that converts an assembly language code to machine code. It
takes basic Computer commands and converts them into Binary Code that Computer's
Processor can use to perform its Basic Operations. These instructions are assembler language
or assembly language.
Example: MASM , TASM
Basic assembler function: (5 basic function)
• Convert mnemonic operation code to their equivalent machine language.
• Convert symbolic operands to their equivalent machine address
• Build machine instruction in the proper format (format 1,2,3,4)
• Convert the data constant to internal machine representation
1
,21CS208 / Operating Systems Unit - I
• Write the object program and assembly listing.
Assembler Directives:
Assembler directives are directions to the assembler to take some action or change a setting.
Assembler directives do not represent instructions, and are not translated into machine code.
It generates instructions by evaluating the mnemonics (symbols) in operation field and find
the value of symbol and literals to produce machine code.
1
Simple sic assembler:
(simplified instructional computer)
Simplified Instructional Computer (SIC) is a hypothetical computer that has hardware
features that are often found in real machines. There are two versions of this machine:
1. SIC standard Model
2. SIC/XE(extra equipment or expensive)
Object programs for SIC can be properly executed on SIC/XE which is known as
upward compatibility
• SIC architecture contains: Memory, Registers, Data format, Instruction
formats, Addressing modes, Instruction set, Input and output
2
, 21CS208 / Operating Systems Unit - I
Below are some examples given below
3
21CS208 – OPERATING SYSTEMS
UNIT I - OVERVIEW OF SYSTEM SOFTWARE
Assemblers & Macro Processors: Simple Assembly Scheme, Pass Structure of assemblers, Macro
Definition and Call, Macro Expansion, Nested Macro Calls, Linkers and Loaders: Introduction,
Relocation and linking Concepts and Types of Loaders.
----------------------------------------------************-----------------------------------------------------
1.1 Assemblers:
System Software is a set of programs that manage the resources of a computer system. System
Software is a collection of system programs that perform a variety of functions.
Definition:
The Assembler is a Software that converts an assembly language code to machine code. It
takes basic Computer commands and converts them into Binary Code that Computer's
Processor can use to perform its Basic Operations. These instructions are assembler language
or assembly language.
Example: MASM , TASM
Basic assembler function: (5 basic function)
• Convert mnemonic operation code to their equivalent machine language.
• Convert symbolic operands to their equivalent machine address
• Build machine instruction in the proper format (format 1,2,3,4)
• Convert the data constant to internal machine representation
1
,21CS208 / Operating Systems Unit - I
• Write the object program and assembly listing.
Assembler Directives:
Assembler directives are directions to the assembler to take some action or change a setting.
Assembler directives do not represent instructions, and are not translated into machine code.
It generates instructions by evaluating the mnemonics (symbols) in operation field and find
the value of symbol and literals to produce machine code.
1
Simple sic assembler:
(simplified instructional computer)
Simplified Instructional Computer (SIC) is a hypothetical computer that has hardware
features that are often found in real machines. There are two versions of this machine:
1. SIC standard Model
2. SIC/XE(extra equipment or expensive)
Object programs for SIC can be properly executed on SIC/XE which is known as
upward compatibility
• SIC architecture contains: Memory, Registers, Data format, Instruction
formats, Addressing modes, Instruction set, Input and output
2
, 21CS208 / Operating Systems Unit - I
Below are some examples given below
3
