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Revision as of 03:57, 30 November 2013 by Diannaa (talk | contribs) (Disambiguated: datum → data | fixed dashes using a script)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)A picture clause is an element in programming languages that is used to describe a datum, 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.
Formatting
A picture clause is made up of various format characters, each of which represents a certain portion of the data item. Each format character can be repeated or followed by a repeat number, which specifies the number of times the format item occurs in the data item. Some examples (from COBOL) are:
| Character | Description |
|---|---|
| A | Alphabetic character (A-Z, a-z, or blank)
|
| B | Blank (space) character |
| CR | Sign indicator ('CR' if negative, blanks if positive)
|
| DB | Sign indicator ('DB' if negative, blanks if positive)
|
| E | Floating-point exponent |
| G | Double-byte (DBCS) graphic/alphanumeric character |
| N | Double-byte (DBCS) character |
| P | Implied scaling digit (not displayed) |
| S | Implied sign (not displayed) |
| V | Implied decimal point (not displayed) |
| X | Any character, alphabetic, numeric, or other symbol |
| Z | Numeric digit, but leading-zero-suppressed (replaced by a blank when equal to zero) |
| 0 | Inserted '0' digit
|
| 9 | Numeric digit (0-9)
|
| / | Inserted '/' character
|
| , | Inserted digit group separator |
| . | Inserted decimal point |
| + | Sign ('-' if negative, '+' if positive)
|
| - | Sign ('-' if negative, blank if positive)
|
| $ | Floating currency sign (blank for leading zeroes, '$' to the left of the most significant digit, otherwise digit 0-9)
|
| * | Floating digit fill ('*' for leading zeroes, otherwise digit 0-9)
|
Examples
Examples from COBOL.
| Picture clause | Data type | Sample values |
|---|---|---|
PIC 999 |
3-digit number | 123, 005, 087, any number from 000 through 999 |
PIC S999 |
3-digit internally signed number | +123, −005, +087, any number from −999 through +999, sign is not displayed |
PIC +999 |
3-digit output signed number | +123, −005, +087, any number from −999 through +999, with sign displayed |
PIC ZZ9 |
3-digit number, leading zeros suppressed | 123, 5, 87, any number from 000 through 999 |
PIC A(8) |
8-character alphabetic string | "Fredrick", "Fred ", "Fred Jr ", any string of 8 alphabetic letters (may include spaces)
|
PIC X(8) |
8-character string | "Smithson", "O'Riley ", "Bon-Jovi", "23Skidoo", any string of 8 characters (may include any valid character)
|
Footnotes
- ^ Non-standard extension provided by IBM and others
- ^ The comma and decimal point can be switched for European use
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