singlestepping

Singlestepping, in computing, refers to the practice of executing a program one instruction at a time. This granular control is mainly used for debugging, education, and detailed observation of how code progresses and how the state of the system changes after each instruction.

How it works

Most hardware and software debuggers implement single-step by invoking a trap or pause after the execution of a single instruction. On hardware, a debug or trap flag in the processor state may cause a debug exception to be raised after each instruction, transferring control to the debugger. Some architectures provide a dedicated single-step instruction. In software simulators and emulators, the interpreter or execution engine can be configured to run exactly one instruction and then halt for inspection.

Applications and limitations

Singlestepping is valuable for understanding control flow, tracking the origin of bugs, and teaching low-level concepts. It reveals exact register values, memory changes, and instruction effects. However, it introduces overhead and can alter timing, especially in multi-threaded or real-time contexts. Some instructions have side effects or take multiple micro-operations that may not be visible in a straightforward one-instruction view. In practice, developers may combine single-stepping with breakpoints, watchpoints, and higher-level debugging features to balance detail and performance.

Examples and terminology

In many debuggers, stepping commands include options to step into a function or step over a call; a variant often specifically named for one-instruction execution is called single-step or step-instruction. Common tools provide commands such as step, step over, and step into to manage execution flow at different granularities.

See also

Single-step execution, Debugging, Step-over, Step-into.