CMS Command and Macro Reference (Rel 6 PLC 17 Apr81)
Page291(291 of 405)
EXEC Control statements Section 5. CMS EXEC Control Statements This section describes the formats, usage rules, and default values for EXEC control words, including: • Control statements • Built-in functions • Special variables An procedure is a CMS file that contains a sequence of CRS commands and/or EXEC control statements. Control statements determine the logic flow for EXEC, provide terminal communications, and may be used to manipulate CMS disk files. For an introduction to the EXEC facilities, and for complete tutorial information, including examples, consult the Guide. EXEC procedures may be invoked with the EXEC command, described in "Section 2. CMS Commands." You may also execute an EXEC procedure by specifying its filename, as long as the implied EXEC function is in effect. section 5. EXEC Control Statements 277
EXEC Control statements-Assignment Statement The Assignment Statement Use the assignment statement in an EXEC procedure to assign a value to a variable symbol. Variable symbols may be tested and manipulated to control the execution of an EXEC procedure. The format of the assignment statement is: r , I I I L- &variable &variable string ae fu nct ion X'xxxxxx I string ae function X'xxxxxx } 1 , I 1 I indicates the variable symbol which is assigned the specified value. A variable may contain a maximum of eight alphameric and national charactersr including the initial ampersand, which is required. Except in the EXEC special variables &* and &DISK*r a variable must not contain any special characters. is a data item of up to eight characters. It may also be a variable symbol or null. Whether a numeric string is treated as numeric or character data depends on how it is used in the EXEC. If a string containing variable symbols expands to more than eight charactersr it is truncated. If the string consists of eight X'FF' characters r the variable is set to a null string. is an arithmetic expression consisting of a sequence of data items that possess positive or negative integral values and are separated by plus or minus signs: &1 - 4 + &CALC - 6 is an built-in function followed by at least one token. indicates up to six hexadecimal digits to be converted to decimal before assignment. For example: &A = X'CO results in &A having the decimal value 192. Hexadecimal conversion is not performed unless you have used the &HEX ON control statement. All variable symbols occurring in executable statements are substituted before the statement is executed. An executable statement is (1) a eMS command liner or (2) an EXEC control statement (including assignment statements) . 278 VM/370 CMS Command and Macro R2ference