HP OpenVMS Systems Documentation

HP OpenVMS DCL Dictionary

Displays the contents of virtual memory.

Requires user-mode read (R) access to the virtual memory location whose contents you want to examine.

Format

EXAMINE location[:location]

Parameter

location[:location]

Specifies a virtual address or a range of virtual addresses (where the second address is larger than the first) whose contents you want to examine. If you specify a range of addresses, separate the beginning and ending addresses with a colon (:).

A location can be any valid arithmetic expression containing arithmetic or logical operators or previously assigned symbols. Radix qualifiers determine the radix in which the address is interpreted; hexadecimal is the initial default radix. Symbol names are always interpreted in the radix in which they were defined. The radix operators %X, %D, or %O can precede the location. A hexadecimal value must begin with a number (or be preceded by %X).

The DEPOSIT and EXAMINE commands maintain a pointer to the current memory location. The EXAMINE command sets this pointer to the last location examined when you specify an EXAMINE command. You can refer to this location using the period (.) in a subsequent EXAMINE command or DEPOSIT command.

Description

The EXAMINE command displays the contents of virtual memory. The address is displayed in hexadecimal format and the contents are displayed in the radix requested, as follows:

address: contents

If the address specified is not accessible to user mode, four asterisks (*) are displayed in the contents field.

Radix Qualifiers: The radix default for a DEPOSIT command or an EXAMINE command determines how the command interprets numeric literals. The initial default radix is hexadecimal; all numeric literals in the command line are assumed to be hexadecimal values. If a radix qualifier modifies an EXAMINE command, that radix becomes the default for subsequent EXAMINE and DEPOSIT commands, until another qualifier overrides it. For example:

$ EXAMINE/DECIMAL 900 00000384: 0554389621

The EXAMINE command interprets the location 900 as a decimal number and displays the contents of that location in decimal. All subsequent DEPOSIT and EXAMINE commands assume that numbers you enter for addresses and data are decimal. Note that the EXAMINE command always displays the address location in hexadecimal format.

Symbol names defined by = (assignment statement) commands are always interpreted in the radix in which they were defined.

Note that hexadecimal values entered as examine locations or as data to be deposited must begin with a numeric character (0 to 9); otherwise, the command interpreter assumes that you have entered a symbol name, and attempts symbol substitution.

You can use the radix operators %X, %D, or %O to override the current default when you enter the EXAMINE command. For example:

$ EXAMINE/DECIMAL %X900 00000900: 321446536

This command requests a decimal display of the data in the location specified as hexadecimal 900.

Length Qualifiers: The initial default length unit for the EXAMINE command is a longword. The EXAMINE command displays data, one longword at a time, with blanks between longwords. If a length qualifier modifies the command, that length becomes the default length of a memory location for subsequent EXAMINE and DEPOSIT commands, until another qualifier overrides it.

Restriction on Placement of Qualifiers: The EXAMINE command analyzes expressions arithmetically. Therefore, qualifiers are interpreted correctly only when they appear immediately after the command name.

Qualifiers

/ASCII

Displays the data at the specified location in ASCII format.

Binary values that do not have ASCII equivalents are displayed as periods (.).

When you specify the /ASCII qualifier, or when ASCII mode is the default, hexadecimal is used as the default radix for numeric literals that are specified on the command line.

/BYTE

Displays data at the specified location, one byte at a time.

/DECIMAL

Displays the contents of the specified location in decimal format.

/HEXADECIMAL

Displays the contents of the specified location in hexadecimal format.

/LONGWORD

Displays data at the specified location, one longword at a time.

/OCTAL

Displays the contents of the specified location in octal format.

/WORD

Displays data at the specified location, one word at a time.

Examples

$ RUN   MYPROG
[Ctrl/Y]
$ EXAMINE   2678
0002678:  1F4C5026
$ CONTINUE
      

In this example, the RUN command begins execution of the image MYPROG.EXE. While MYPROG is running, pressing Ctrl/Y interrupts its execution, and the EXAMINE command displays the contents of virtual memory location 2678 (hexadecimal).

$ BASE = %X1C00
$ READBUF = BASE + %X50
$ ENDBUF = BASE + %XA0
$ RUN   TEST
[Ctrl/Y]
$ EXAMINE/ASCII READBUF:ENDBUF
00001C50:  BEGINNING OF FILE MAPPED TO GLOBAL SECTION
   .
   .
   .
      

In this example, before executing the program TEST.EXE, symbolic names are defined for the program's base address and for labels READBUF and ENDBUF; all are expressed in hexadecimal format using the radix operator %X. READBUF and ENDBUF define offsets from the program base.

While the program is executing, pressing Ctrl/Y interrupts it, and the EXAMINE command displays in ASCII format all data between the specified memory locations.