My file is about Fetch and Executive stages of processing. The processor contains a single data register, called the accumulator (AC). Both instructions and data are 16 bits long, and memory is organized as a sequence of 16-bit words. The instruction format provides 4 bits for the opcode,allowing as many as 24  16 different opcodes (represented by a single hexadecimal3 digit). The opcode defines the operation the processor is to perform.With the remaining 12 bits of the instruction format,up to 212  4096 (4 K) words of memory (denoted by three hexadecimal digits) can be directly addressed.