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Revision as of 16:32, 20 February 2008 by Loadmaster (talk | contribs) (→Structure: converted to table, removed incorrect text about sign 'S')(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)A picture clause is an element in programming languages that is used to describe a data item, by using sample characters that indicate the item characteristics and size.
History
The picture clause was first used in the COMTRAN (Commercial Translator) language developed by Bob Bemer of IBM in 1957. In 1959, it was incorporated into the original definition of COBOL. Since then, many other programming languages have copied this feature.
Structure
A picture clause is made up of various characters, each of which represents a certain type of data item. The number of repeated characters indicates the size of the data item. Here are some examples (from COBOL) of picture characters and what they represent:
| Character | Description |
|---|---|
| A | Alphabetic character (A-Z, a-z, blank) |
| B | Blank (space) character |
| X | Any character, alphabetic, numeric, or other symbols |
| 9 | Numeric digit (0-9) |
| Z | Numeric digit, but leading-zero-suppressed (replaced by a blank when equal to zero) |
| S | Implied sign for a number |
| V | Implied decimal point |
| , | Digit group separator |
| . | Decimal point |
| + | Sign ('-' if negative, '+' if positive) |
| - | Sign ('-' if negative, blank if positive) |
Examples
| picture clause | data type | sample contents |
|---|---|---|
| PICTURE IS 999 | 3-digit number | 123, 005, 087, any number from 000 through 999 |
| PICTURE IS S999 | 3-digit internally signed number | +123, -005, +087, any number from -999 through +999 |
| PICTURE IS +999 | 3-digit output signed number | +123, -005, +087, any number from -999 through +999, with sign displayed. |
| PICTURE IS ZZ9 | 3-digit number, leading zeros suppressed | 123, 5, 87, any number from 000 through 999 |
| PICTURE IS A(8) | 8-character alphabetic string | "Fredrick", "Fred ", any string of 8 alphabetic letters (may include spaces) |
| PICTURE IS X(8) | 8-character string | "Smithson", "O'Riley ", "Bon-Jovi", "23Skidoo", any string of 8 characters (may include spaces) |