- Flow of control:
- Flow of control = the flow (path) of the execution of a computer program
Normally, the computer will execute the next instruction after it finishes executing the current instruction
EGTAPI can stop the execution temporarily to let you examine the content of the registers and variables
(This will help you understand the inner workings of a computer)
- Terminology:
breakpoint
- Breakpoint =
a location in the
program where
execution will be
temporarily halted when the
program execution arrives at
that location
A breakpoint must always be marked by an .global label in the program
- Breakpoint =
a location in the
program where
execution will be
temporarily halted when the
program execution arrives at
that location
- You can set a
breakpoint at the
location in your
program at an
.global label as
follows:
- Sample assembler program:
.global Start, Stop, CodeEnd, DataStart, DataEnd .global A, B, C .global X Start: move.l A,d0 move.l B,d1 X: add.l d1,d0 ** We set a breakpoint at this program location move.l d0,C nop nop Stop: nop A: dc.l 4 B: dc.l 15 C: ds.l 1 End: endHow to set a breakpoint at the .global label X:
- Type the name of the
label
(X) into the
"Breakpoint Name" field:
- Type the name of the
label
(X) into the
"Breakpoint Name" field:
- Click on the
Add button:
You will see X appear in the Breakpoint window.
- Sample assembler program:
- Fact:
- When you reload the running program, the breakpoints will be reset to the breakpoints specified in the EGTAPI startup file
- You can save the
breakpoints that you have
added as
follows:
- Click on the "Save Debug" button below the Breakpoint window
- EGTAPI provide
2 ways to
control the
flow of execution of
the program:
- Step (located at the
top-right corner in the
EGTAPI window)
Effect of the Step button:
- EGTAPI will
execute the
current instruction and
stop
The next instruction will become the new current instruction
(When EGTAPI stops, it will display the current values of the registers and memory variable values)
So you can use the Step button to examine the effect of the execution of the current instruction
- EGTAPI will
execute the
current instruction and
stop
- Run (located
next to the
Step button)
Effect of the Run button:
- EGTAPI will
execute instructions
in the program
until the execution
reaches (= arrives) at a
breakpoint
The (new) current instruction will be the instruction at the breakpoint
(When EGTAPI stops, it will display the current values of the registers and memory variable values that were updated by many instructions !!!)
You use the Run button to complete of the execution of a segment of code quickly
- EGTAPI will
execute instructions
in the program
until the execution
reaches (= arrives) at a
breakpoint
- Step (located at the
top-right corner in the
EGTAPI window)
- If the
assembler program is
correct, you can
run the
program by:
- Load the
program into
EGTAPI
- Click on the "Run" button
- Load the
program into
EGTAPI
- Run:
- Before you can use the
Run button, you need to
set a
breakpoint at a location
(= label) in your program
that your program will
"pass" during its
execution
- Use the Run button to reach the breakpoint location in your program.
- Before you can use the
Run button, you need to
set a
breakpoint at a location
(= label) in your program
that your program will
"pass" during its
execution
- Step:
- Use the Step button to
check whether the
program instructions that you
wrote are
correct (or not):
- Execute each instruction one at a time
- Check if the result of the execution is what you had intended
- Use the Step button to
check whether the
program instructions that you
wrote are
correct (or not):