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### 25.1 TUI Overview

In TUI mode, gdb can display several text windows:

command
  This window is the gdb command window with the gdb prompt and the gdb output. The gdb input is still managed using readline.
source
  The source window shows the source file of the program. The current line and active breakpoints are displayed in this window.
assembly
  The assembly window shows the disassembly output of the program.
register
  This window shows the processor registers. Registers are highlighted when their values change.

The source and assembly windows show the current program position by highlighting the current line and marking it with a ``>`' marker. Breakpoints are indicated with two markers. The first marker indicates the breakpoint type:

`B`
  Breakpoint which was hit at least once.
`b`
  Breakpoint which was never hit.
`H`
  Hardware breakpoint which was hit at least once.
`h`
  Hardware breakpoint which was never hit.

The second marker indicates whether the breakpoint is enabled or not:

`+`
  Breakpoint is enabled.
`-`
  Breakpoint is disabled.

The source, assembly and register windows are updated when the current thread changes, when the frame changes, or when the program counter changes.

These windows are not all visible at the same time. The command window is always visible. The others can be arranged in several layouts:

- source only,
- assembly only,
- source and assembly,
- source and registers, or
- assembly and registers.

These are the standard layouts, but other layouts can be defined.

A status line above the command window shows the following information:

target
  Indicates the current gdb target. (see Specifying a Debugging Target).
process
  Gives the current process or thread number. When no process is being debugged, this field is set to `No process`.
function
  Gives the current function name for the selected frame. The name is demangled if demangling is turned on (see Print Settings). When there is no symbol corresponding to the current program counter, the string `??` is displayed.
line
  Indicates the current line number for the selected frame. When the current line number is not known, the string `??` is displayed.
pc
  Indicates the current program counter address.