The Simplified Instructional Computer
is a hypothetical computer
described in Leland Beck
's book System Software
. Most real microprocessors have a complex instruction set and many subtleties to increase efficiency. These can be a distraction for students that are studying the essential and universal aspects of a microprocessor
that are common to different designs. The architecture uses 3 byte integers, 5 registers and can access 215
=32768 bytes of memory.
The five registers are as follows:
- A register (accumulator): This is the one-byte register that stores the address of the variable.
- X register (index): The index register can operate in two modes, direct and indexed.
- SW register (status word)
- PC register (program counter)
- L register (linkage): This register is used for subroutine jumps.
Negative values are stored in 1's complement format. The SIC has two versions: a standard version, SIC, and an extended version, SIC/XE. The extended version has floating point numbers.