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One of the best-known software errors occurred on 22 July 1962 when the Mariner I rocket had to be blown-up, after it followed an erratic path after it took off. It was caused by a single incorrect character in a FORTRAN statement for the motion equations.

In 1963, ANSI defined the 7-bit ASCII standard code for characters. At the same time IBM had developed the 8-bit EBCDIC code which allowed for up to 256 characters, rather than 128 characters for ASCII. It is thought that the 7-bit code was used for the standard as it was reckoned that eight holes in punched paper tape would weaken the tape. Thus the world has had to use the 7-bit ASCII standard, which is still popular in the days of global communications.
Key characters to remember are:
'A' 41h 0100 0001
'a' 61h 0110 0001
'0' 30h 0011 0000

LF 0Ah 0000 1010
CR 0Dh 0000 1101

Mastering Comput-ing, W.Buchanan, Palgrave

Isn't that interesting?

 


 


 

 

 

 

 

 

 

Booking holidays: Client-server or peer-to-peer

8 July 2001 WORK IN PROGRESS!

n important concept in Computing is the differentiation between a peer-to-peer connection and a client-server connection. With a client-server connection, servers provide services to clients, and must wait for clients to connect to these services. Typical services might be to allow the printing of documents to a shared printer, or provide access to a networked file system. A peer-to-peer architecture allows for two systems to actively seek connections, without involving a server. An example of a client-server network in human terms might be a travel agent, who will wait for customers (clients) to get in contact with them in order to book the best holiday for them. The clients contact the agents (servers) to book a holiday, who will then find the best holiday for them. A peer-to-peer network would be equivalent to someone phoning a friend (who isn't a travel agent) and asking them of the best holiday that they could get. The friend might then go and book the holiday over the Internet. This is a peer-to-peer network, as the friend does not actively seek questions on holiday arrangements, or in booking holidays.

Chapter 5, Mastering Computing, W.Buchanan, Palgrave.

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