System information

4.2.4 The G (Go) Command

A program is executed using the G command, with up to two optional breakpoint addresses. The

G command takes the forms:

Gs,b

Gs,b,c

G,b

G,b,c

The first form executes the program at the current value of the program counter in the current

machine state, with no breakpoints set. The only way to regain control in DDT is through a RST

7 execution. The current program counter can be viewed by typing an X or XP command.

The second form is similar to the first, except that the program counter in the current machine

state is set to address s before execution begins.

The third form is the same as the second, except that program execution stops when address b is

encountered (b must be in the area of the program under test). The instruction at location b is not

executed when the breakpoint is encountered.

The fourth form is identical to the third, except that two breakpoints are specified, one at b and

the other at c. Encountering either breakpoint causes execution to stop and both breakpoints are

cleared. The last two forms take the program counter from the current machine state and set one

and two breakpoints, respectively.

Execution continues from the starting address in real-time to the next breakpoint. There is no

intervention between the starting address and the break address by DDT. If the program under

test does not reach a breakpoint, control cannot return to DDT without executing a RST 7

instruction. Upon encountering a breakpoint, DDT stops execution and types

4.2 DDT Commands CP/M Operating System Manual

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