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PUNCHED CARDS:

PUNCHED CARDS

What is punched cards? :

What is punched cards? Punched cards are an old input (sometimes output) medium for communicating with mainframes. Bits were represented by punching holes in the right places, the job performed by a keypunch machine which had an alpha keyboard.

ORIGIN:

ORIGIN As early as 1725 Basile Bouchon used perforated paper loop in a loom to establish the pattern In 1726 his co-worker Jean- Baptiste Falcon improved on his design by using perforated paper cards attached to one another. The Bouchon -Falcon loom was semi-automatic and required manual feed of the program. Joseph Jacquard used punched cards in 1801

TWO TYPES OF PUNCHED CARDS::

TWO TYPES OF PUNCHED CARDS: EIGHTY COLUMN CARD NINETY SIX COLUMN CARD

EIGHTY COLUMN CARD:

EIGHTY COLUMN CARD Divided from left to right into 80 vertical columns. Each column can be represented as one character Top three rows are zone punching positions and left rows are numeric punching positions

HOLLERITH CODE:

HOLLERITH CODE Herman Hollerith was the first person who used punched cards. This coding system is known as Hollerith code after his name.

NIGHTY SIX COLUMN CARD:

NIGHTY SIX COLUMN CARD One third the size of 80 column card Upper portion is used as print area Round holes instead of rectangular holes Standard six bit code is used instead of hollerith code Has six punch positions and remining 4 are numeric positions

FUNCTIONAL DETAILS:

FUNCTIONAL DETAILS The method is quite simple: On a piece of light-weight cardboard, successive positions either have a hole punched through them. The rectangular bits of paper punched out are called chads or chips. Thus, each punch location on the card represents a single binary digit (or "bit").

DATA PROCESSING:

DATA PROCESSING Unit record equipment for punching and printing the cards was manufactured. Allowed complicated data processing tasks to be achieved An electrical or optical sensor is used to detect the position of hole on card High-speed mechanical feeders to process 100 of cards per minute

ADVANTAGES:

ADVANTAGES Punch cards that held processing instructions were called control cards Cards are standardized Can be used with any hardware system Easily read by humans Easy to handle Old and a habituated ,reliable medium Multi purpose media, they can be used for input, output and storage

Obsolescence:

Obsolescence Punched-card systems fell out of favour in the mid to late 1970s Disk storage became cost effective, and affordable interactive terminals Users could edit their work with the computer directly Many programs still operate on this convention Newer systems employ graphical user interfaces with variable-width type fonts

Hanging Chad:

Hanging Chad

IBM PUNCHED CARD FORMAT:

IBM PUNCHED CARD FORMAT Standard Format held 80 columns representing 80 characters. Only numeric information was coded with 1 or 2 punches per column Later, codes were introduced for upper-case letters and special characters. Cards were 7 and 3/8 inches long by 3 and 1/4 inches high 0.007 inch thick with one of the upper corners cut at an angle.

KEY PUNCH:

KEY PUNCH Data was entered on a machine called a keypunch, which was like a large, very noisy typewriter. Often the text was also printed at the top of the card, allowing humans to read the text as well.

LIMITATIONS:

LIMITATIONS Even all the columns of card are punched, data density of the card is quite small. Card cannot be erased and reused to enter new data . Quite costly and operate at very slow speed. Can’t stored for a long duration of time

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