String Instructions in 8086 8086 Microprocessor by Ravinder Nath Rajotiya - December 14, 2020May 10, 20210 String Related Instructions A string is nothing but a collection of ascii Characters codes. Many a time it require to perform some operation on strings such as copy a string, compare strings, concatenation of strings etc. 8086 has a powerful set of string related instructions and are DIscussed below: REP GROUP: Instructions Description Example FLAG affected REP It is used as a prefix instruction. Repeat until CX=0, REP decrements CX in each loop REPE / REPZ Repeat the instruction until CX=0 or ZF is not equal to 1. REPE prefix will cause string instruction to be repeated, as long as compared bytes or words are equal or CX is not zero. GenerALly used with CMPS and SCAN REPNE / REPNZ Repeat the following instruction until the compared string are not equal, and CX
Instruction Set 8086 8086 Microprocessor by Ravinder Nath Rajotiya - October 14, 2020April 28, 20210 Platforms for writing 8086 assembly programs. Assembly level language program for the 8086 processors can be written in the following platforms. Directly as hex codes fed into the RAM and executed on a trainer kit DOS debug utility of windows Writing the text file in notepad or gedit and then assembling using the MASM, TASM, NASM assemblers etc. We can also write and run the program in the IDE of C or C++ Classification of instructions 8086 instructions may be classified as: Classification based on size of the instruction: As discussed in topic on instruction format 8086 instruction can be from 1 to 6 byte long. The first two bytes indicate the OPCODE and the addressing Classification based on the addressing modes: The