DECLARING 2 DATA ITEMS AND REPRESENTATION

Transcription

1 DELARING 2 DATA ITEMS AND REPRESENTATION hapter SYS-ED/ OMPUTER EDUATION TEHNIQUES, IN.

2 Objectives You will learn: How to declare PL/I variables with scale, base and mode. Internal representation of numeric, character and varying character strings. Differences between the number types and which types to use for a particular circumstance. Declaring and using bit strings. How to initialize a variable in the DELARE statement. How to format data items for printing or for writing to a dataset. How to code the PITURE specification in a DELARE statement. SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page i

3 1 Declare of Arithmetic Data T = total digits F = fractional digits Terminology Keywords Attributes Base Scale Precision Length Vocabulary that makes up the PL/I language. Descriptive properties of data. Radix of a value (DEIMAL or BINARY) Fixed-point or Floating-point Number of digits in an arithmetic value. Number of characters in alphanumeric data or number of bits in a bit-string. SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 1

4 1.1 Fixed Decimal Declare DL DOLLARS_AND_ENTS FIXED DEIMAL (15,2); DL PERENT FIXED DEIMAL (7,4); DL NET_PROFIT FIXED DE (13,0); 1.2 Fixed Binary Declare DL TABLE_INDEX FIXED BINARY (15,0); DL VERY_HIGH_OUNTER FIXED BIN (31,0); SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 2

5 2 Floating Point Declaration Example: DL SPEED FLOAT DEIMAL(6); This declare is used to reserve a floating point number with six significant digits being maintained. Since precision is less than seven digits, short form floating point is used (4 bytes). Example: DL VERY_PREISE_NUMBER FLOAT DE(16); This declare is used to reserve a floating point number that requires more than 6 significant digits to be maintained. Sixteen digits of precision are reserved for this variable. Long form floating point is used (8 bytes). SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 3

6 3 Arithmetic Data Types Data Type Use Precision Maximum Value Used for FIXED BINARY (15,0) (31,0) 32,767 2,147,483,647 counting. array indexing. representing integers. FIXED DEIMAL (t,f) where: Up to 15 digits numbers with fractional parts. t=total digits f=fractional digits and t should be an odd data where total accuracy is required (e.g. Payroll. larger numbers FIXED BINARY cannot be accommodated. FLOAT DEIMAL 3 sizes: (6) Short (16) Long (33) Extended 10**75 extremely large or small numbers. most modeling and scientific programming. convenience (PL/I will maintain the significant digits). SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 4

7 4 Declaration of Strings Examples: DL NAME HAR(20); DL TRUE BIT (1); DL ITY HARATER(16); SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 5

8 5 Varying Length Strings Format: DL NAME HAR(30) {VARYING} {VAR} Strings may have the VARYING attribute. Allows the string to take on different lengths. Length can vary between 0 and maximum specified in DELARE. PL/I internally tracks the string length automatically. It uses 2 extra bytes (halfword binary) added to the front of the string's storage to store the length. SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 6

9 6 Initial Attribute The initial attribute is used to give starting values to variables when storage is assigned. Format: DL identifier attribute(s) {INITIAL} (value or expr.); {INIT} Examples: DL NAME HAR(10) DL TOWN HAR(20) DL FALSE BIT(1) DL ATTR BIT(4) INIT('ALBERT'); [padded with 4 blanks] VAR INIT ('AFTON'); [stores length] INIT ('O'B); INIT ('101101'B); [truncates rightmost 2 bits] DL DOLLAR_AND_ENTS FIXED DE(7,2) INIT ( ); DL LARGE_NUMBER FLOAT DE(16) INIT ( ); DL RD_OUNT FIXED BIN(15,0) INIT (9 or FIXED BIN(15,O) INIT (1001B); SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 7

10 7 String Data DATA TYPE STORED LENGTH HARATER_STRING 1 HARATER PER BYTE 0 TO HAR's BIT_STRING 8 BITS PER BYTE 0 TO BITS DL NAME HAR(20), MASK BIT(17) String data may have the varying attribute in which case the actual length at any particular time is the length of the last data item assigned to it. DL NAME HAR(20) VARYING; NAME = 'JON'; /*LENGTH IS 3 BYTES */ NAME = 'JONATHON'; /*LENGTH IS 8 BYTES */ SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 8

11 8 Exercise AVERAGE: PROEDURE OPTIONS(MAIN); DELARE (A,B,,D,E) FIXED(4,1); GET LIST (A,B,,D,E); MEAN = (A+B++D+E) / 5; PUT LIST('AVERAGE IS', MEAN); END AVERAGE; Explicitly Declared Identifiers Implicitly Declared Identifiers SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 9

12 9 Declaring Identifiers with the Bit Attribute DELARE YES BIT(1), NO BIT(1), MORE_TRANSATIONS BIT(1), SKILLS BIT(16); YES = '1'B; NO = '0'B; MORE_TRANSATIONS = YES; SKILLS = ' 'B; SKILLS = (8)'0B' ** (8)'1'B; Pad on right with zeros if bit-string is less than the declared length. Truncate on right if bit-string is greater than the declared length. SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 10

13 10 Initial Attribute The initial attribute causes an identifier to be set (initialized) to a specified value before execution of other PL/I statements in a program. DL TITLE DL DELETE DL SUM HAR(10) INITIAL('SIT GEORGE'); HAR HAR(1) INIT(' '); FIXED(5) INIT(0); DL PI FIXED(6,5) INIT( ); /* NOTE ABBREVIATION */ DL (A,B,) FIXED(3) INIT(0); DL ON DL OFF BIT(1) INIT('1'B); BIT(1) INIT('0'B); SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 11

14 11 Picture Attribute SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 12

15 12 Picture haracters 9 ANY DEIMAL DIGIT V VIRTUAL DEIMAL POINT (AUSES DEIMAL POINT ALIGNMENT). DEIMAL POINT INSERT (NOT NEESSARILY RELATED TO DEIMAL POINT ALIGNMENT) - NEGATIVE (USUALLY USED ON OUTPUT PITURES) 9 POSITIVE (USUALLY USED ON OUTPUT PITURES) s X A SIGN--POSITIVE OR NEGATIVE (USED FOR INPUT AND OUTPUT) ANY ALPHANUMERI HARATER ANY ALPHABETI HARATER $ INSERT DOLAR SIGN 0 INSERT ASTERISK, INSERT OMMA B R DB Z INSERT BLANK HARATER (USUALLY USED ON OUTPUT PITURES) REDIT SYMBOL (R FOR NEGATIVE FIELDS, bb FOR POSITIVE FIELDS) DEBIT SYMBOL (DB FOR NEGATIVE FIELDS, bb FOR POSITIVE FIELDS) ZERO SUPPRESS (INPUT: BLANKS, INTERPRETED AS ZEROS, OUTPUT: LEADING ZEROS REPLAED BY BLANKS.) / INSERT SLASH SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 13

16 SOURE DATA PITURE SPEIFIATION RESULTING DATA '99999' 'ZZZZ9' '99V.99' 'ZZV.ZZ' 'ZZV.99' 'ZZ.V99' '9999V.99' 'ZZZZV.99' 'Z,ZZZV.99BBB' '99/99/99' 'Z9/99/99' 'ZZ/ZZ/ZZ(5)B' '$ZZZ,ZZZV.99' '$$$$,$$$V.99cr' '999V.99' 's999v.99' '999V.99BDB' '999V.99R' '999V.99S' '(6)A' bbbb bbbbb bb.00 bbb b bb123.45bbb 07/07/84 b7/07/84 b7/b7/84bbbbb $bb1, bb$1,200.75bb bDB R ABbbb SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 14

17 13 Declare Statement Formats FORMAT 1: DL AMT_OF_PURHASE FIXED DE(7,2) INIT(0); DL AMT_OF_OST FIXED DE(7,2) INIT(0); DL AMT_REEIVED FIXED DE(7,2) INIT(0); FORMAT 2: DL AMT_OF_PURHASE FIXED DE(7,2) INIT(0), AMT_OF OST FIXED DE(7,2) INIT(0), AMT_REEIVED FIXED DE(7,2) INIT(0); FORMAT 3 (FATORING): DL (AMT_OF_PURHASE, AMT_OF_OST, AMT_REEIVED) FIXED DE(7,2) INIT(0); FORMAT 4 (FATORING): DL (AMT_OF_PURHASE INIT(300.00), AMT_OF_OST INIT(250.00), AMT_REEIVED INIT(0) FIXED DE(7,2); SYS-ED \OMPUTER EDUATION TEHNIQUES, IN. (113-PL/I: 01.3) h 2: Page 15