What is a Punch Card?
Paper cards with holes punched into them to represent computer data and instructions are known as punch cards (or "punched cards"), Hollerith cards, or IBM cards. They were a common way for people to enter data into early computers. The cards were put into a card reader that was attached to a computer, which translated the holes' order into digital data.
For instance, an early computer programmer might write a program by hand, then use a punch card machine to convert it to multiple punched cards. The programmer would then bring the stack of cards to a computer and input the software there using a card reader.
History of the punch card
Punch cards were reportedly used to operate textile mills as early as 1725. As an illustration, Joseph Marie Jacquard utilized punch cards to weave a silk self-portrait. Semen Korsakov utilized the cards in 1832 to store and look up information. Herman Hollerith created a mechanism for machines to record and store data on punch cards later in 1890, which was used for the US census. Later, he founded the business that would become IBM.
How were punch cards operated?
By punching holes in each column, which stands for one character, using a punch card machine like the one in the image above, data can be entered into the card.
When a card is finished, or the Return key is pushed, the information is technically "stored" on the card. If you develop a program using punch cards (one card for each line of code), it requires a stack of cards because each card can only carry so much data.
Each card is placed in a punch card reader to read the data from the card and load the software into the computer. The punch card reader begins reading the card as soon as it is inserted, moving vertically from top to bottom. The card reader advances to the following column after reading one column. The information would be written to a computer's memory as the reader read it. The computer would be told to run the code when all cards had been loaded into memory. Punch cards would be produced as information was output (printed).
The SAGE air defense system from the 1950s, which utilized 62,500 punched cards, was the most extensive punch card program (around 5 MB of data). The punch cards used in this application are seen in the image below with a woman standing next to them.
Dropping the punch cards was one of the customers' primary concerns when using them. It might take days or weeks to get the program back in working order if these cards were dropped or went out of order. It might not be feasible to restart the software in some circumstances.
How is a punch card read by a person?
The contents of each card were generally printed at the top of later punch cards. To see what was saved on these cards, you might look at the top of the card. The card would be reprinted if an error was found on it. If the top of the card was blank, the human would have to figure out what each number on it meant and manually translate each column. If you are familiar with modern computers, this is comparable to knowing that the binary values 01101000 and 01101001 are equivalent to 104 and 105, respectively, which, when combined in ASCII, spells out the letter hi.
Why did people utilize punch cards?
Unlike modern computers, early computers could not store files. Punch cards were the sole means to use data with other computers if you wanted to create a data file or software. Punch cards were no longer used after magnetic media was developed and became more affordable.
Are Punch cards still in use?
In the early 1900s, punch cards were the main tool for storing and retrieving data. Punch cards were first replaced by other storage technologies in the 1960s, and today they are seldom ever used or seen.
Are Punch cards their inputs?
No. The cards are not input devices by themselves. However, because it transfers data from the punch card to the computer, the punch card reader is regarded as an input device.
How were punch cards programmed, and why were punch cards chosen?
Punch cards and other pre-existing technology, such as paper tape, were utilised. Originating with early methods of vote counting in 1890. The IBM 401 from 1933 was a design that was highly reminiscent of those used in subsequent computers. The punch card reader was the IBM407, I believe, when I first used them in the middle of the 1960s. Similar to paper tape, it was employed because it was a readily adaptable existing technology. Regarding the language, I used FORTRAN IID, with the D standing for the computer's new-fangled disc storage system. However, the bootstrap code for the IBM1130 was also stored on punched cards and was loaded directly into memory.
What did punch card coding feel like?
Much more effective than it is now, in the final years of punched cards, I took a FORTRAN course, albeit I didn't do it professionally. For each programme, we had three attempts to get it properly. Like hitting the RUN button only three times, Even I was astonished that I was able to complete most of the 25 programmes in just two attempts before using the third run to either try something new or improve the output formatting.
This is the method I used. On the coding sheet, carefully code the program's initial try. Get the printout from the first run; compilation mistakes would be clear. Do not instantly debug it; instead, take it home and manually run it using the printout. Then on the printout, note each error and make the necessary corrections. Pick each incorrect card one at a time, up until the column where it belongs. After that, make the necessary corrections, which are on the card. Next time, bring it back to the computer centre. We used a machine for rectification that we had to operate ourselves.
Place the indicated card and a new card, then use the copy button to move both to the appropriate column. When the automatic machine was overloaded, we occasionally had to physically punch on a manual Hollerith code machine by twisting our fingers. The machine looked similar to this, but to make things more challenging, it only had numbers instead of the letters displayed in this picture.
Has a C compiler been created that outputs to punch cards?
You may use any existing compiler for any language to feed data into a punched card reader, then read the cards back into a compatible computer and run the programme. Punched cards are a data storage system. The same logic applies to determining whether memory sticks or hard drives require a different compiler than punched cards. The type of data storage is unimportant.
How did punch cards store non-digital computer data?
Punch cards ARE digital, so I'm not sure what you mean when you say "non-digitally." similar to how magnetic tape or magnetic discs are. On a light paper card, the bits are represented by holes placed in precise locations. Lights that either doesn't shine through where there isn't a hole or don't shine through where there is a hole are passed by the card. That data is digital. Magnetic fields on media can reverse or not, which is how discs operate. In both of these examples, the data is digital, but the actual world objects are analogue. Analogue phenomena exist in all of reality. In this sense, punch cards are just another type of digital data storage.
What did the remaining six bits per column on punch cards perform
An excellent joke first. How was Herman Hollerith interred after his passing? 9-edge right, inverted the punch card for an electronic tabulating machine was initially created by Hollerith (for a detailed history, search "Hollerith" on Google). This is why it is (to some of us) so amusing. You would place the stack of cards with the 9-edge facing down and either to the right (or left) of the card reader (or up). The explanation Thomas provided for the "holes" was excellent.
You would use the entire 80-column card if you were representing data. You had to adhere to the Cobol constructs (code in columns 8–72; column 6 for the comment character and column 72 for continuation if necessary) if you were using it for Cobol code. Initially used an IBM 026 punching machine. In those days, there was no hanging chad, so you could remove the chad and deface someone's room (I digress). Sequencing was performed on Col 73–80. The more recent card punch devices would automatically sequence your cards for you.
Therefore, you could run your cards through a card sorter if you dropped your deck or if a stupid operator shuffled your cards. I can assure you that you don't want to manually sort a programme with 1000 cards, according to Cobol constructions cols.