Chapter 4: Data dependent branching/Absolute Addressing

Question 1

What is data dependent branching?

Answer 1

If/Else structures are often used in high level languages to do operations dependant on data values. An example of a simple if structure is shown below. An if/else structure requires additional branches to ensure the else block is only executed if the condition is not true.

Question 2

Example pseudocode for a conditional loop?

Answer 2

Question 3

Example code for a if/else loop?

Answer 3

Question 4

What is Absolute addressing?

Answer 4

Absolute addressing means that the destination address for the jump is given in the instruction.

Question 5

Problems with absolute addressing?

Answer 5

However the difficulty with this addressing mode is that there is often not enough space within the instruction for the full address.

Question 6

Absolute addressing, methods to get around the problem of not having enough space to store the full address?

Answer 6

Solutions to this problem could be to restrict the range of the destination address, so that the upper bits of the programme counter are unchanged; or reduce the resolution of the address by omitting the lower bits and assuming that they are zero.