Immediate
  Immediate (6502)
    LDA #23 - copy the value 23 into the accumulator.

  Immediate (IBM 360)
    LA R1,41(0) - IBM 360 does not support pure immediate, however it is
                  possible to use base displacement with r0.

  Immediate base displacement (IBM 360)
    MVI 42(R15),C'$'
      Move the value '$' into a specified memory location.
        SI type instruction - 4 bytes long.
        1st byte is opcode.
        The binary value for characer '$' symbol is store 
          as 2nd byte of instruction.
        bits 16-19 Register, 20-31 Displacement

    ICM R1,B'1001',23(R2) - fetches 1st and 4th byte from the memory
       block starting at the address specified by 23(R2). Although the
       bits that hold B'1001' are supposed to name a register they are 
       instead interpreted as a mask (an operand immediately available 
       upon fetching of the complete instruction.