Vintage Computer Programming of 1970s

These are the basic specs of three computing devices that I used during different periods of my lifetime:

1. 128 KB main memory, 29MB disk drive
2. 8GB main memory, 1TB hard disk
3. 4GB RAM, 64GB storage

The last one is the smartphone I carry in my pocket today and I don't have to describe the various tasks one uses it for, as these days everyone carries one to run different Apps.

The second one above is the laptop sitting on my desk which is primarily used for producing nicely formatted documents that include photos, videos, spreadsheet calculations, project schedules, and other parts.

The top one in the list is not the IBM PC I used in 1987 but actually the mainframe computer that I worked with during 1972-1982 while I was in ISRO at Trivandrum and at Ahmedabad. Many of my colleagues will still remember this workhorse, the ‘IBM 360 Model 44 PS’ that occupied a room the size of a basketball court.

IBM System 360 Computer with tape drives

IBM Disk Pack

IBM Punch Card Reader

The IBM 360 Model 44 was announced in August 1965 and withdrawn in September 1973.

It would be just amazing for the present generation to know that this room-full of a computer had just 128 KB of main memory (yes KB, not MB!) and its 29 MB hard disk (yes MB, not GB!) was a replaceable pack of around 14" size in diameter that needs to be carried with both hands to be mounted on the disk drive! 

But then we used it for such wonderful compute intensive tasks such as the structural analysis of satellite launch vehicles (SLV) requiring inversion of 100 x 100 matrices, the development of digital and photographic products of data acquired by remote sensing satellites (Bhaskara), etc. It also had, as auxiliary storage, magnetic tape drives that used 0.5-inch wide, 2,400 feet long removable magnetic tape reels of 10.5 inches diameter.

Compare that with the extravagant 8GB RAM and 1TB 2.5" hard drive of my laptop! Or with the bountiful 4GB RAM and 64GB storage of my mobile phone! And you get a fairly good idea about the enormous increase in memory size and the phenomenal reduction in physical size that our generation of senior citizens has experienced in a lifetime!

In those days we would write the FORTRAN program by hand on a paper, then convert the program to several 80-column punched cards using a Punch Card machine, which you will be lucky to find in a computer museum today. Programs were basically decks of such punch cards. The resulting deck of cards would be picked up by the computer operator and fed into a card reader to be compiled. Depending upon the number of jobs in the queue, the results of your job would be available after a few hours or the next day, and not instantly as we are used to now.

With such a long turnaround time for each task you cannot afford to make even a syntax error, let alone logical errors. On top of it you have to have a very tight design of your program to work within the extremely limited hardware resources available to you. 

Computer programming in those days was a real challenging task as well as very fulfilling.

See the comments of this original Facebook post.