Discuss the differences between SIC and SIC/XE machine architectures with regard to: i)Registers ii) Instruction formats

i) Registers:

• SIC: The Simplified Instructional Computer (SIC) has five registers, each of 3 bits. These are the Accumulator (A), the Index register (X), the Linkage register (L), the Program Counter (PC), and the Status Word (SW).
• SIC/XE: The SIC/XE (SIC Extended) has an additional five registers, making a total of ten. These are the Base register (B), the General Purpose registers (S, T, F), and the Input/Output registers (I/O). The General Purpose and I/O registers are not present in the standard SIC.

ii) Instruction Formats:

• SIC: SIC uses a fixed format of 24 bits for instructions. The first 8 bits are for the operation code (opcode), the next 1 bit is for the indexing address flag, and the remaining 15 bits are for the address.
• SIC/XE: SIC/XE uses a variable format for instructions, which can be 1, 2, 3, or 4 bytes long. The first byte is for the opcode and flags, the second byte (if present) is for the displacement or address, and the third and fourth bytes (if present) are for the address or data. This allows for more complex and diverse instructions than the standard SIC.