programming techniques: Looping,counting,Indexing

1. B.RAMA PRABHA,
ASSISTANT PROFESSOR,
DEPARTMENT OF COMPUTER SCIENCE,
K.C.S.KASI NADAR COLLEGE OF ARTS & SCIENCE,
CHENNAI-21

2. Programing Techniques:
Looping
Counting
Indexing

3. Looping :
The programming technique used to instruct the
microprocessor to repeat tasks is called looping.
A loop is set up by instructing the microprocessor to
change the sequence of execution and perform the task
again.
This process is accomplished by using Jump
instructions.
In addition, techniques such as counting and indexing
are used in setting up a loop.

4. Loops can be classified into two groups
1. Continuous loop: Repeats a task continuously
2. Conditional loop: Repeats a task until certain data
conditions are met.

5. Continious Loop
Repeats a task
continuously.
A continuous loop is set
up by using the
unconditional jump
instruction
A program with a
continuous loop does not
stop repeating the tasks
until the system is reset.
start
Perform task
Go back and Repeat

6. CONDITIONAL LOOP
 A conditional loop is set up by a conditional jump
instructions.
 These instructions check flags(Z,CY,P,S) and repeat the
tasks if the conditions are satisfied.
 These loops include counting and indexing.

7. Counting and Conditional Loop
 A counter is a typical application of the
conditional loop.
 A microprocessor needs a counter, flag
to accomplish the looping task.
 Counter is set up by loading an
appropriate count in a register.
 Counting is performed by either
increment or decrement the counter.
 Loop is set up by a conditional jump
instruction.
 End of counting is indicated by a flag.
Start
Setup a counter
for five tasks
• Tasks
performed
• Decremented
counter by 1
If
counter
=0?
Stop
No
Yes

8. Indexing
 Another type of loop includes indexing with counter.
Indexing means pointing or referencing objects with
sequential numbers.
Similarly data bytes are stored in memory location
and those data bytes are referred to by their memory
location

9. Example:
Steps to add ten bytes of data stored in memory locations starting
Data given location and display the sum.
The microprocessor needs a counter to count 10 data bytes.
An index or a memory pointer to locate where data bytes are stored.
To transfer data from a memory location to the icroprocessor(ALU)to
perform addition.
Registers for temporary storage of partial answers a flag to indicate
the completion of the stack to store or output the result.