First Day Class (Assembler E-Learning Course)

ajaychandra · New User Joined: 31 Mar 2005 Posts: 16 Location: Bangalore

Hi Friends,

This is the first day class...... (e-learn) Check every day..

HIGH LEVEL ASSEMBLER

INTRODUCTION:

ASSEMBLER is a symbolic programming language that lies closet to the machine language in form and contents. Therefore the assembler language is useful when

1) You need to control the program closely, down to byte and even bit level.
2) You must write subroutines for functions that are not provided by other symbolic languages like COBOL, PL/I

The assembler language is made up of statements that represents either instructions or comments. The instruction statements are working part of the language and are divided into the following three groups.

1) Machine Instructions : A machine instruction is a symbolic representation of machine language instructions. It is called a machine instruction because the assembler translate it into machine language code that the computer can run.
2) Assembler Instructions : An Assemble instruction is a request to assembler to do certain operations during the assembly of a source module. The assemble doesn't translate the assembler instructions into object code.
3) Macro Instructions : A macro instruction is a request to a assembler program to process a predefined sequence of instructions called macro definitions. From the definition assembler generates Machine and Assembler Instructions, which it then process as if they were part of original input in source module. IBM supplies some macro definitions for input/output, data management, supervisory operations that you can call for processing. You can prepare your own macro and call by coding corresponding macro instruction.

Assembling and Link-editing your Assembler Language Program

The Program written in Assembler Language becomes the source module that is input to the assembler. The assembler process the source module and produces an object module in machine language(called object code).The object module can be used as input to be processed by linker or binder. The linker or binder produces the load module which can be loaded into main storage later. When program is loaded then it can be run.

The source module, object code and other information are printed in program listings.

Processing Sequence

The Assembler process the machine and assembler instructions at different times during its processing sequence. The assemble processes most of the instructions twice, first during conditional assembly and later at assembly time.

Conditional Assembly and Macro Instructions:

The assembler process the conditional assembly instructions and macro processing instructions during conditional assembly. During the processing the assembler evaluates arithmetic, logical and character conditional assembly expressions. Conditional assembly takes place before assembly time.

The assembler processes the macro instructions at assembly time.

"Any suggestions are welcome"

priya · Posted: Mon Apr 18, 2005 5:20 pm

Great work Ajay Chandra Reddy, Keep it up!!! :

prasannanjaneya · New User Joined: 14 Mar 2005 Posts: 10 Location: pune

hi,
can u please explain much more detail about processing sequence. i think this will comes at the time of compiling or like-editing. and please explain the operation of assembler in the system in detail.

thank u,
prasanna.

sinusam · New User Joined: 06 Jan 2004 Posts: 18

HI ajay,

You have done great work by providing these much information.

I have a problem. I need to read and write a sequential file through Assembler (DSORG = PS).

I tried to do it with DCB macro..but lot of problems... please help me.

Regards,
Sinu

priya · Posted: Thu Apr 28, 2005 2:14 pm

Start a new Topic...

parikshit123 · Active User Joined: 01 Jul 2005 Posts: 269 Location: India

Hmmm,

Great work..
I will definitely attend each days class.

thanks again.

anandana10 · New User Joined: 29 Jul 2005 Posts: 3

Hi Ajay,

Your article is of definely a great help for starters like me. Please could you tell if there is any simulator available for OS/390 for windows so that I could do some programs practically....

Thanks,

Anandana

yogeshpawar · New User Joined: 01 Mar 2006 Posts: 37 Location: Sussex-UK

You can give a try for PC370 for assenbler programs which is good tool on desktop