--- title: "COBOL: Indexed BY Vs USAGE Vs OCCURS" description: "In COBOL, Index data items, OCCURS, and KEY clauses are tricky. Explained the benefits and usage of these items with examples." url: https://srinimf.com/2015/07/20/mainframe-cobol-occurs-indexed-byusage-is-index-1-of-2/ date: 2015-07-20 modified: 2026-10-10 author: "Srini" image: https://i0.wp.com/srinimf.com/wp-content/uploads/2015/07/usage-is-index.jpg?fit=1200%2C700&ssl=1 categories: ["COBOL"] tags: ["COBOL Index", "COBOL OCCURS", "COBOL Usage"] type: post lang: en --- # COBOL: Indexed BY Vs USAGE Vs OCCURS The COBOL occurs, Usage is Index, Indexed By clause are tricky. And these are confused by many people. In this post, I have shared three key points: 1. OCCURS 2. Indexed BY 3. Usage is Index --- ### 1). COBOL Occurs [COBOL programmers](http://www.indeed.com/jobs?q=CICS+DB2&indpubnum=6634974704162507) confused very much about [how to](https://srinimf.com/2011/05/12/cobol-multi-dimension-arrays/) use the OCCURS clause with the KEY phrase correctly. The syntax** for OCCURS clause with **Indexed BY ``` 01 GROUP-ITEM. 03 ITEM-A OCCURS 7 TIMES INDEXED BY IX. 05 NAME PIC X(20). 05 ADDRESS-1 PIC X(20). 05 ADDRESS-2 PIC X(20). 05 ADDRESS-3 PIC X(20). 05 CITY PIC X(20). 05 STATE PIC XX. 05 ZIP PIC 9(5). … PERFORM VARYING IX FROM 1 BY 1 UNTIL IX > 7 DISPLAY NAME(IX),CITY(IX),STATE(IX),SPACE,ZIP(IX) END-PERFORM. ``` ### 2). COBOL Index Indexed is different from the index data item (Usage is an index). [This post gives you a complete idea](https://srinimf.com/2015/07/21/5-key-differences-of-index-and-subscript-for-cobol-programmers/). **About Index in TABLE ARRAY** - An index name (or just index) is an item that contains a value corresponding to an occurrence number of the table with which it is associated. - Index(IX) is not necessarily stored in memory as an integer. - A COBOL vendor may choose to implement it as a pointer to an element of the table, an offset from the beginning of the table, or whatever representation seems convenient for a particular COBOL implementation. - The purpose of the index is to make accessing a table as efficiently as possible. **In simple words:** - The index is different from the Index data item - The index is not required to define explicitly in the COBOL program - The index is associated with a Table on which it is mentioned - The index is not an identifier. So, the index is not an Integer - Index names you can use as variables in PERFORM, SET, and SEARCH Statements You are now good with what is an index. Now, I will share the key points on what is an index data item. ### 3). Usage is Index Data Item: ``` 01 INDEX-1  USAGE is INDEX. or 77 INDEX-1  USAGE is INDEX. ``` Related[Best Example for COBOL SEARCH and WHEN Condition](https://srinimf.com/2016/01/06/best-example-for-cobol-search-and-when-condition/) Benefits of Usage is Index Data item 1. Number one benefit is, you can pass the Usage-is-index data item to a SUBPROGRAM (the **indexed-value** you cannot pass to the sub-program) 2. The other benefit is, you can write the usage-is-index data items to a file. 3. How we use Index the same way you can use usage is an index data item. **How to Display Usage is Index data item** ``` DISPLAY INDEX_1. ``` ### 4). How to Define Key ``` Ascending/Descending Key is XYZ. ``` **Table definition with Multiple KEYS:** ``` 01 MAIL-INFO. 03 MAIL-LIST OCCURS 1000 TIMES ASCENDING KEY IS STATE, CITY. 05 NAME PIC X(20). 05 ADDRESS PIC X(20) OCCURS 3 TIMES. 05 CITY PIC X(20). 05 STATE PIC XX. 05 ZIP PIC 9(5). ``` **Interview Question on Keys:** - By specifying ascending/descending Key IS, it doesn’t mean that the Table is in sorted order. This is only an expected order. Also read - [COBOL: How to Create a VB Array](https://srinimf.com/2020/04/26/cobol-how-to-create-a-vb-array/)DateApril 26, 2020 - [How to Define VB files in COBOL Sample Logic](https://srinimf.com/2012/03/29/cobol-arrays-variable-files/)DateMarch 29, 2012 - [COBOL: How to Define Key in Array](https://srinimf.com/2015/03/24/cobol-use-of-key-phrase-in-occurs-clause/)DateMarch 24, 2015 ### Share this: - - [Tweet](https://twitter.com/share) - [![](https://i0.wp.com/assets.pinterest.com/images/pidgets/pinit_fg_en_rect_gray_20.png)](https://www.pinterest.com/pin/create/link/?url=https%3A%2F%2Fsrinimf.com%2F2015%2F07%2F20%2Fmainframe-cobol-occurs-indexed-byusage-is-index-1-of-2%2F&media=https%3A%2F%2Fi0.wp.com%2Fsrinimf.com%2Fwp-content%2Fuploads%2F2015%2F07%2Fusage-is-index.jpg%3Ffit%3D1200%252C700%26ssl%3D1&description=COBOL%3A%20Indexed%20BY%20Vs%20USAGE%20Vs%20OCCURS) - - [Share on Tumblr](https://www.tumblr.com/share) - [Share on WhatsApp (Opens in new window) WhatsApp](https://srinimf.com/2015/07/20/mainframe-cobol-occurs-indexed-byusage-is-index-1-of-2/?share=jetpack-whatsapp) - [More](#) - - [Print (Opens in new window) Print](https://srinimf.com/2015/07/20/mainframe-cobol-occurs-indexed-byusage-is-index-1-of-2/?share=print) - [Share on Reddit (Opens in new window) Reddit](https://srinimf.com/2015/07/20/mainframe-cobol-occurs-indexed-byusage-is-index-1-of-2/?share=reddit) - [Share on Telegram (Opens in new window) Telegram](https://srinimf.com/2015/07/20/mainframe-cobol-occurs-indexed-byusage-is-index-1-of-2/?share=telegram) - [Email a link to a friend (Opens in new window) Email](mailto:?subject=%5BShared%20Post%5D%20COBOL%3A%20Indexed%20BY%20Vs%20USAGE%20Vs%20OCCURS&body=https%3A%2F%2Fsrinimf.com%2F2015%2F07%2F20%2Fmainframe-cobol-occurs-indexed-byusage-is-index-1-of-2%2F&share=email) - ### Like this: Like Loading…