Subtitles of the Movie

The IBM Mainframe Assembly Language is quite different because the architecture of the CPU is different. It has 16 general purpose 32-bit registers. They're identified by the numbers zero through 15 and it has four 64-bit floating point registers. The condition codes set by comparison operation is only two bits in size. There are some other status bits but only two are used as condition codes. It has a separate location that holds the 31-bit instruction address but the most dramatic difference is that there is no stack. If you want to perform any stack operations, you'll have to simulate the stack by using a general purpose register and a block of memory. Normally, when a function is called, it is a responsibility of that called function to include a block of memory and store the registers in that block and then restore them for the return. And some things have different meanings than you might be accustomed to. A byte is still eight bits long and the addresses work the same as you're used to. Adding one to an address moves the location by one byte. It is limited but it's possible to do some things with 16-bit values. They're called half-word. A word, the natural link for the machine, is four bytes, 32-bits and a double word is 64 bits. Certain types of data must be aligned on addresses of these sizes. But the assembler lines them up for you. It will insert fillers only if necessary. A summary of the assembly language instructions and a few other things are printed on what is known as a green card that's supplied as part of the documentation. You really can't program this Assembly Language without one. For different versions of the machine, the green card is different colors. But the actual color doesn't matter; they always call it the green card.