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Questions and Answers
What is the primary purpose of a macro instruction?
What is the primary purpose of a macro instruction?
What is the output of a macro processor?
What is the output of a macro processor?
When are macros handled by the assembler?
When are macros handled by the assembler?
What is the key difference between a macro and a subroutine?
What is the key difference between a macro and a subroutine?
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What is the role of a preprocessor in a macro processor?
What is the role of a preprocessor in a macro processor?
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What is the relationship between the macro name and its expansion?
What is the relationship between the macro name and its expansion?
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What is the major disadvantage of using subroutines?
What is the major disadvantage of using subroutines?
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What is the purpose of the macro preprocessor statement?
What is the purpose of the macro preprocessor statement?
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What is the syntax of a macro call?
What is the syntax of a macro call?
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What is the purpose of the MACRO directive?
What is the purpose of the MACRO directive?
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What is the effect of macro processing on the resulting code?
What is the effect of macro processing on the resulting code?
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What is the purpose of the MEND directive?
What is the purpose of the MEND directive?
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Study Notes
Macro Instructions
- Macro instructions are single-line abbreviations for groups of instructions.
- For every occurrence of a macro instruction within a program, the instruction must be replaced by the entire block.
Advantages of Macros
- Simplify and reduce the amount of repetitive coding.
- Reduce the possibility of errors caused by repetitive coding.
- Make an assembly program more readable.
Macro Processors
- A preprocessor can be any program that processes its input data to produce output, which is used as an input to another program.
- The outputs of the macro processors are assembly programs that become inputs to the assembler.
- The macro processor may exist independently and be called during the assembling process or be a part of the assembler implementation itself.
Difference between Macro and Subroutine
- Macro name in the mnemonic field leads to expansion only.
- Macro is completely handled by the assembler during assembly time.
- Subroutine name in a call statement in the program leads to execution.
- Subroutines are completely handled by the hardware at runtime.
- Macro definition and macro expansion are executed by the assembler.
- Hardware executes the subroutine call instruction.
Macro Definition and Call
- A macro consists of a name, a set of formal parameters, and a body of codes.
- A macro can be defined by enclosing a set of statements between a macro header and a macro end statement.
- The formal structure of a macro includes:
- Macro prototype statement: specifies the name of the macro and name and type of formal parameters.
- Model statements: specify the statements in the body of the macro from which assembly language statements are to be generated during expansion.
- Macro preprocessor statement: specifies the statement used for performing auxiliary function during macro expansion.
- A macro can be called by writing the name of the macro in the mnemonic field of the assembly language.
- The syntax of a typical macro call can be of the following form:
[ [,…]]. - The MACRO directive in the mnemonic field specifies the start of the macro definition.
- The MEND directive specifies the end of the macro definition.
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Description
Learn about macro instructions, their advantages, and how they simplify and reduce repetitive coding in assembly programming. Understand how macro processors work and their role in preprocessing.
