File handling in PL/1

Steps in PL/1 file program.

Define File

Open the file

Read File

Process the data till end of file.

Close the file.

Define File( Declaring a file in PL\1)

Record in the data set are referenced by the file name in PL\1File name can be 1-8 characters long.E.g. DCL user_file file input record env(F recsize(80));dcl outreport output stream env(F blksize(80));dcl printrpt output stream print env(F blksize(80));

Explanation for the attributes.

Type of transmission  “STREAM’ or “RECORD”

If you are using structures like group variables in cobol in your programm to handle the data you have to use the “RECORD”

Direction of the transmission “INPUT” “OUTPUT” and “UPDATE”

Physical environment( Attributes of physical dataset)

This specifies the attributes of the dataset. It can also be mentioned in jcl.

env(F recsize(80)

Above statement says that the data set is fixed block and the logical record length is 80.

OPEN FILE

Syntax:

open file(file_name);

eg. open(inp-file);

open(inpfile1,user_file);

we can also specify input/output , stream/record, print, pagesize, linesize.

List directed IO in PL/1

You can use list directed I/O method to read/write datasets if you  used stream while declaring the file (   dcl outreport output stream env(F blksize(80));   )

GET

get file(file_name) list(variable list);

get file(file_name) edit(variable list);

PUT

put file(file_name) list(variable list);

put file(file_name) edit(variable list);

RECORD INPUT/OUTPUT

Provides extreme flexibility for file handling. Widely used in many science and business application.

You must use RECORD type of transmission while declaring the file.

eg. dcl report_input file record env(F recssize(80));

RECORD I/O Statements

read file(file_name) into(record_area);

e.g. read file(user_data) into(user_structure);

write file(file_name) from(record_area);

e.g. write(user_data) from(user_structure);

FILE I-O program in PL\1

 FILEIO:PROCEDURE OPTIONS(MAIN);                                   
 /*                                                                
 PROGID. FILEIO                                                    
 AUTHOR. SHIBU THANNIKUNNATH                                       
 DATE  . 2011-FEB-12                                               
 COMMENT                                                           
 */                                                                
  /*DECLARE */                                                     
  DCL 1 USER_DETAILS,                                              
        2 NAME                         CHAR(15),                   
        2 AGE                          CHAR(02),                   
        2 ADDR                         CHAR(15),                   
        2 STREET                       CHAR(15),                   
        2 CITY                         CHAR(15),                   
        2 COMMENT                      CHAR(18);                   

  %PAGE;                                                           
  DCL INP_CTR                          FIXED DEC(2) INIT(00);      
  DCL INP_FILE_EOF                     BIT INIT('1'B);             
  DCL USERFLE                          FILE INPUT RECORD ENV(F     
  %SKIP;                                RECSIZE(80));              
  /*OPEN FILE*/                                                    
  OPEN FILE(USERFLE);                                              
  ON ENDFILE(USERFLE) INP_FILE_EOF='0'B;                           
  READ FILE(USERFLE) INTO(USER_DETAILS);                           
  /*DO UNTIL EOF*/                                                 
  DO WHILE(INP_FILE_EOF);                                          
    INP_CTR=INP_CTR+1;                                             
    PUT SKIP LIST('REC#'||INP_CTR);                                
    PUT SKIP LIST('NAME '||NAME||'AGE '||AGE||'ADDR1 '||ADDR||     
                  'STREET '||STREET||'CITY '||CITY||'COMMENT '||   
                  COMMENT);                                        
    READ FILE(USERFLE) INTO(USER_DETAILS);                         
  END;                                                             
  END FILEIO;

OUTPUT