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COBOL Tutorial Conti...
FILES: File is nothing but a logical name which represents a memory location to store the data permanently in a structured way. o Files are stored in DISKS/TAPES. o Maximum 255 files used in COBOL program. o ORGANIZATION Clause is used to define a file. Hierarchy of file: In the hierarchical manner, file can be defined as a set of records which are stored as a instances/ occurances. Records can be defined as a combination of fields which are defined a sequence. Fields can be defined as a collection of information which needs to be stored. TYPES OF FILES: o Sequential files (data is entered in sequential order) o Indexed files (data is entered based on key sequential order) o Relative files ( data is entered based on RRN ( Relative Record Number)) SEQUENTIAL FILES: o Sequential file records are read from top to bottom but bottom to top is not possible. o Specific record reading is not possible in sequential files. o Sequential files are also called as flat files, QSAM files, non-VSAM files. INDEXED FILES: o Retrieving of data is faster in indexed files. o Random accessing of data is done in indexed files based on key ( ex: bank a/c no) o Data accessing is faster in indexed files. o Data arranged in sorted order based on key.
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