Chapter 4- Machine Language Flashcards
What is the name of the program that translate assembly code to binary code?
Assembler
What are the 3 options to specify and address in assembly code?
- Direct accessing: express a specific address or use symbol for that address- LOAD R1,67 // R[1] <- 67
- Indirect addressing: address mode to handle pointers. The instruction specifies memory location that holds the required address
Indirect addressing example: x = foo[j];
Write it in assembly
Add R1, foo,j // R1 = foo+j
LOAD R2,R1
STR R2, x
What is the hack computer?
16 bit machine builds from CPU, two memory modules- instruction memory and dat memory and two memory mapped i/o devices.
It also has two registers: D and A. They ar 16 bit
What is the instruction memory?
It is a read only memory of size 32k 16 bit words
What D register is used for?
To store data.
What A is used for?
Data register and address register. Means as address In the data memory or address in the instruction memory.
For the instruction memory, jump operations always effect a jump to the instruction located In the memory address by A.
Goto 35, first set A to 35 and then just goto command
What is M?
Memory access instructions operate on an implicit memory location labeled M.
M always refers to the memory word who’s address is the current value of A.
D =Memory[516] - 1 so first set A = 516 and then D = M - 1;
What is @value
Store value in A. It is the A instruction
How many commands to I need when memory location is involved?
Two: one for selecting the address and the second is to operate on the memory location of that address.
Because of that there is the A instruction and the C instruction
To compute
What M stands for?
memory[A]
What is the format of C instruction?
111a ….
How to increment memory[7] and also store it in D?
@7
MD=M+1
What is a prequisiof a jump?
That A register holds the value of the instruction line to jump to.
If there is a jump we should avoid using
Register M because it can get conflicted with the A register that holds the place to jump.
What is the location of the base memory of the screen?
- It has 8k rows
How is each screen line represented in the computer and from where?
From to left. Each row has 32 16bit arrays. Pixel in Row r from the top and column c from the left is: Mapped to c%16 bit of the array in RAM[16384 + r*32 + c/16]
What is the address of the keyboard and how Does it map?
The address is 24576 and each time a key is pressed, the ASCII of the key appears at memory[24576]
What is (symbol)?
It’s a pseudo command that causes the assembler to assign the label symbol to the memory location in which the next command of the program will be stored. It generated NO machine code
