Programming in COBOL-85 For IBM Mainframe System 390 Jyothi Sridhar Kini E&R, Infosys Mail-id: Jyothis@infosys.com Phone: 52179 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Objectives of the Session (1) Index sequential file organization. (2) Relative file organization. (3) The COPY verb. (4) The CALL verb. (5) Demonstration of sample programs. 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Indexed file organization Essentially comprises of two files namely (1) A data file and (2) An index file. Provides both sequential and random access. Slowest of all types of file organizations. Facilitates the use of multiple alphanumeric keys. Moderately storage efficient. 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Example Data File Index File BU103 Roopa 19 BU101 Deeptha 20 REGNO NAME AGE BU103 Roopa 19 BU101 Deeptha 20 BU102 Bhavana 18 Index File REGNO ADDRESS BU101 00a3c2 BU102 00a3d4 BU103 00b943 Index 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Indexed and Relative Files 1/14/2019 9:43 AM E&R Dept., ITLInfosys

ED Entries for Indexed Files [ ] ENVIRONMEN T RANDOM DYNAMIC DIVISION . INPUT - OUTPUT SECTION FILE CONTROL SELECT LogicalFN ] FileName ASSIGN TO FileS pec ORGANIZATI ON IS INDEXED ACCESS MODE IS SEQUENTIAL RECORD KEY IS U niqueRecKe y ALTERNATE RECORD KE Y IS AltKe WITH DUPLICATES STATUS IS File Status ì í î ü ý þ ï é ë ê ù û ú 1/14/2019 9:43 AM E&R Dept., ITLInfosys

About index sequential file An indexed file in Cobol can be accessed either sequentially or randomly. When accessed randomly, the sequence in which the records are accessed can be specified by the data item called record key 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Prime key and alternate key The field which is specified in the RECORD KEY clause is known as prime key Alternate key for the file can be specified using the ALTERNATE KEY clause Alternate keys are unique by default If the file has duplicate values for the alternate key then WITH DUPLICATES phrase should be specified 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Indexed File Verbs OPEN INPUT OUTPUT I-O FileName ì í ï î ü ý þ 1/14/2019 9:43 AM E&R Dept., ITLInfosys

READ To read the records in the file in direct fashion To read the records in the file in sequential fashion 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Write and Rewrite The records are written to the logical position as determined from the value of the record key REWRITE statement requires that the file must be opened in the I-O mode 1/14/2019 9:43 AM E&R Dept., ITLInfosys

DELETE The record last read by the READ statement is deleted in case of sequential read In case of random read the record to be deleted is specified in the record key option File must be opened in the I-O mode 1/14/2019 9:43 AM E&R Dept., ITLInfosys

START statement The START positions the file to the first logical record whose record key satisfies the condition specified by the key phrase The access mode must be SEQUENTIAL OR DYNAMIC File must be opened in the I-O or input mode. 1/14/2019 9:43 AM E&R Dept., ITLInfosys

START 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Relative Files 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Select and Assign for Relative Files

Relative File Verbs All the verbs discussed with INDEXED files holds good in Relative Organization too. Point to remember is that relative key is not part of Relative record and is declared as WS variable and must contain proper values.

File ORGANIZATIONs - A comparative study SEQUENTIAL INDEXED RELATIVE Slow when the hit Slowest Direct Access Wasteful of storage hit rate is low. organization if the file is only partially populated. Complicated to Especially slow while Complicated to change. (Insert, adding or deleting of program. Delete). records. 1/14/2019 9:43 AM E&R Dept., ITLInfosys

File ORGANIZATIONs - A comparative study SEQUENTIAL INDEXED RELATIVE Simplest Can use multiple, Only a single, ORGANIZATION. Alphanumeric keys numeric key is allowed. Most storage Not very storage Least storage efficient. efficient. Efficient. 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Demonstration of Sample Programs 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Break 1/14/2019 9:43 AM E&R Dept., ITLInfosys

COPY Verb The COPY is executed at compile time unlike other COBOL verbs which are executed at run time. The COPY statement allows programs to include frequently used source code text from a copy file or a copy library. The COPY can include source code text with or without change into the client program. Each client program which wants to use items described in the copy library uses the COPY verb to include the descriptions it requires. 1/14/2019 9:43 AM E&R Dept., ITLInfosys

COPY Verb Examples (1) COPY “EMPLOYEE-RECORD”. (2) COPY ”STUDENT" REPLACING ABC BY XYZ. 1/14/2019 9:43 AM E&R Dept., ITLInfosys

COPY Example IDENTIFICATION DIVISION. PROGRAM-ID. COPYEG1. AUTHOR. JYOTHI SRIDHAR. ENVIRONMENT DIVISION. FILE-CONTROL. SELECT StudentFile ASSIGN TO "STUDENTS” ORGANIZATION IS SEQUENTIAL. DATA DIVISION. FILE SECTION. FD StudentFile. COPY COPYFILE. PROCEDURE DIVISION. A0001-MAIN-PARA. -------- --------- STOP RUN. Copy member resides in OPERN.CICS3.COPYLIB 01 Student. 88 EndOfSF VALUE HIGH-VALUES. 02 StudentNumber PIC 9(7). 02 StudentName PIC X(60). 02 CourseCode PIC X(4). 02 FeesOwed PIC 9(4). 02 AmountPaid PIC 9(4)V99. 16

CALL Verb Is the most important verb that provides structured programming capabilities in COBOL. Is equivalent to a function or a sub-routine call in other computer languages. Is similar to the COPY verb, in the sense that it provides code re-usability. Provides two ways of passing parameters to the called program (1) By REFERENCE and (2) By CONTENT. 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Syntax of call statement CALL NAME OF THE SUB PROGRAM USING THE PARAMETER NAMES Example CALL SUBPGM1 USING NUM1,NUM2 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Passing by reference and value CALL SUBPGM1 USING WS-NUM1. BY VALUE CALL SUBPGM1 USING BY CONTENT WS-NUM1 BY REFERENCE WS-NUM2 BY REFERENCE WS-NUM3. 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Rules for coding CALLed Programs DATA DIVISION. WORKING –STORAGE SECTION. ---- LINKAGE SECTION. 01 WS-NUM1 PIC 9(3). 01 WS-NUM2 PIC 9(3). PROCEDURE DIVISION USING WS-NUM1,WS-NUM2 DATA DIVISION. WORKING –STORAGE SECTION. ---- LINKAGE SECTION. 01 WS-NUM1 PIC 9(3). 01 WS-NUM2 PIC 9(3). The CALLed programs should have a LINKAGE SECTION in the DATA DIVISION. If the CALLed programs possess WORKING-STORAGE SECTION, then the LINKAGE SECTION must appear after it. The PROCEDURE DIVISION of the CALLed program must have a USING clause to identify the variables passed from the CALLing program. 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Rules for coding CALLed Programs DATA DIVISION. WORKING –STORAGE SECTION. ---- LINKAGE SECTION. 01 WS-NUM1 PIC 9(3). 01 WS-NUM2 PIC 9(3). PROCEDURE DIVISION USING WS-NUM1,WS-NUM2. A001-MAIN-PARA. ----- EXIT PROGRAM The variables defined in the LINKAGE SECTION can be defined in any order. The variables in the USING clause must be in the same order as in the CALL statement of the CALLing program. Instead of a STOP RUN statement, the CALLed program must contain an EXIT PROGRAM statement to transfer the control back to the CALLed program. 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Review Index sequential file organization. Relative file organization. The COPY verb. The CALL verb. 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Review questions DELETE statement should be followed by ( file/record) _________ For updation and deletion, the files are to be opened in ___________________ mode COPY statement is allowed only in the data division ( True / false ) Indicate which of the following COBOL verb does not use FROM phrase ACCEPT DISPLAY PERFORM WRITE File name Input-output (I-O) 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Review Questions LINKAGE SECTION cannot have any value clause (True / False ) RENAMES clause cannot be used in LINKAGE SECTION (True / False ) COPY statement is executed during compile time rather then run time ( True/ False) 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Any Questions ???? 1/14/2019 9:43 AM E&R Dept., ITLInfosys

Thank you Jyothi Sridhar Kini E&R, Infosys Mail-id: Jyothis@infosys.com Phone: 52179 1/14/2019 9:43 AM E&R Dept., ITLInfosys