The following three terms described below are part of the expanded data processing cycle.
1. Origination:
In this step original data is collected on certain documents which are known as the source documents. For example student record (roll no., name, address, marks, class, age). In case of error this original document is referred. During processing some information is required or some information is to be written on the storage.
2. Storage:
During processing some information is required or some information is to be written then the storage is used. For example the no. of students who passed with different grades. This information is to
be written the stored information is used for further purpose.
3. Distribution:
In this step the output is distributed to the different departments according to their requirement. For example income tax statement is sent to the income tax department. The output of one system becomes the input for the other. In the above example the income tax department receives income tax report from various departments and prepares a summary from this report and sends it to the finance division.
The terms mentioned below are also related to the expanded data processing cycle and in my view should also be understood by the students.
Card Reader:
The data can be fed to the computer by using a card reader. The data is punched in the form fo holes. When the card is read by the computer the light passes through the holes which is sensed by the computer and the data is stored in the computer memory. One card contains 80 columns and 12 rows.
Tape Drive:
The data can be fed to the computer by using a magnetic tape which is mounted in the tape drive. The width of the tape is ½” to 1”. The length of the tape is 1200 feet to 2400 feet.
Before the data can be written on the magnetic tape it is mounted in the tape drive. System checks the tape. In the case of errors system indicates the errors. This step is known as tape initialization.
While the data is written on the tape the tape moves on the heads. Usually there are two spools (reels). One is known as feeding spool or supply reel and the second is known
as take up spool or take up reel. For reading the data similar action is repeated and the data is read by the read head.
Inter Block Gap (IRG):
When a record is written on the magnetic tape due to the momentum of the tape the tape can not stop suddenly and strops after some time. Due to which a gape occurs between each record which is known as Inter Record Gap or IRG. It is usually ½”.
Inter Block Gap (IBG):
The IRG cannot be reduced but to overcome this there is a term known as Inter Block Gap (IBG). If the records are blocked then the gap after each block is known as Inter Block Gap. Assume there are 100 records and each block contains 10 records then there will be 9 IBGs. In this case about 5” of tape is wasted. In the case of IRG 50” of tape is wasted.
Advantages of Blocking:
1. It saves space on the magnetic tape by reducing IRG.
2. Computer time is saved. Assume there are 10 records on the magnetic tape. If we read the sequentially one record will load in the memory and processed. The reading of the record from the tape or disk is known as physical read. Reading from the memory is called logical read. In case of IRG there will be 100 physical and 100 logical reads. If the IRG is blocked 10 records per block then in one read 10 records are read. Similarly there will be 10 physical and 10 logical reads due to which the time of the computer is saved.