A command string is the complete specification of a debugger
    command. Although you can continue a command on more than one
    line, the term command string is used to define an entire command
    that is passed to the debugger.

    A debugger command string consists of a verb and, possibly,
    parameters and qualifiers.

    The verb specifies the command to be executed. Some debugger
    command strings might consist of only a verb or a verb pair. For
    example:

    DBG> GO
    DBG> SHOW IMAGE

    A parameter specifies what the verb acts on (for example, a file
    specification). A qualifier describes or modifies the action
    taken by the verb. Some command strings might include one or more
    parameters or qualifiers. In the following examples, COUNT, I,
    J, and K, OUT2, and PROG4.COM are parameters (@ is the "execute
    procedure" command); /SCROLL and /OUTPUT are qualifiers.

    DBG> SET WATCH COUNT
    DBG> EXAMINE I,J,K
    DBG> SELECT/SCROLL/OUTPUT OUT2
    DBG> @PROG4.COM

    Some commands accept optional WHEN or DO clauses. DO clauses are
    also used in some screen display definitions.

    A WHEN clause consists of the keyword WHEN followed by a
    conditional expression (within parentheses) that evaluates to
    true or false in the current language. A DO clause consists
    of the keyword DO followed by one or more command strings
    (within parentheses) that are to be executed in the order that
    they are listed. You must separate multiple command strings
    with semicolons (;).  These points are illustrated in the next
    example.

    The following command string sets a breakpoint on routine SWAP.
    The breakpoint is triggered whenever the value of J equals 4
    during execution. When the breakpoint is triggered, the debugger
    executes the two commands SHOW CALLS and EXAMINE I,K, in the
    order indicated.

    DBG> SET BREAK SWAP WHEN (J = 4) DO (SHOW CALLS; EXAMINE I,K)

    The debugger checks the syntax of the commands in a DO clause
    when it executes the DO clause. You can nest commands within DO
    clauses.