What is the meaning of near and far declaration in microprocessor programming using C?

Answer 1

Programs that are loaded into memory typically have several segments associated with them: the Code Segment (CS), the Stack Segment (SS), the Data Segment (DS), sometimes an Extended Segment (ES), and almost always a Block Started by Symbol (BSS) segment. This question requires that we focus only on the Code Segment (CS). The CS is a segment of memory that contains some of the instructions that are required for the program to execute. If this segment is not large enough to contain the whole program then the program can be loaded into different segments. Such a segment may be 64Kb in size (although the size may differ). Instructions located in these segments are referred to by their offset from the start of the segment, and not by their absolute location in memory. Thus, in order to locate a certain instruction, we need the segment's starting address, and the offset of the instruction in that segment. Whenever a branch (jump, goto) takes place which refers to an instruction that is located in another segment, it is known as a far jump, conversely whenever a jump refers to an instruction that is located in the same segment, it is known as a near jump. The difference referring to the modication of the CS register which contains the address of the current Code Segment for the current running program.