Source : WordNet®

complex instruction set computer
     n : (computer science) a kind of computer architecture that has
         a large number of instructions hard coded into the cpu
         chip [syn: {complex instruction set computing}, {CISC}]
         [ant: {reduced instruction set computing}, {reduced
         instruction set computing}, {reduced instruction set
         computing}]

Source : Free On-Line Dictionary of Computing

Complex Instruction Set Computer
     
        (CISC) A processor where each instruction can perform several
        low-level operations such as memory access, arithmetic
        operations or address calculations.  The term was coined in
        contrast to {Reduced Instruction Set Computer}.
     
        Before the first RISC processors were designed, many computer
        architects were trying to bridge the "{semantic gap}" - to
        design {instruction set}s to support {high-level language}s by
        providing "high-level" instructions such as procedure call and
        return, loop instructions such as "decrement and branch if
        non-zero" and complex {addressing mode}s to allow data
        structure and {array} accesses to be compiled into single
        instructions.
     
        While these architectures achieved their aim of allowing
        high-level language constructs to be expressed in fewer
        instructions, it was observed that they did not always result
        in improved performance.  For example, on one processor it was
        discovered that it was possible to improve the performance by
        NOT using the procedure call instruction but using a sequence
        of simpler instructions instead.  Furthermore, the more
        complex the instruction set, the greater the overhead of
        decoding an instruction, both in execution time and silicon
        area.  This is particularly true for processors which used
        {microcode} to decode the (macro) instruction.  It is easier
        to debug a complex instruction set implemented in microcode
        than one whose decoding is "{hard-wired}" in silicon.
     
        Examples of CISC processors are the {Motorola} {680x0} family
        and the {Intel 80186} through {Intel 486} and {Pentium}.
     
        (1994-10-10)