For 2023 - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.
Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!
I am also active in many other area and still look after a lot of web sites - you can find an index ((here))
Integer types, and integer overflows, in C
C offers you the ability to define a whole variety of integer types:
short int my_number;
long int my_number;
typically occupying 16, 32 and 64 bits of memory (but that is NOT a standard, and you may find different on some systems). And the amount of memory that's declared controls the minimum and maximum numbers that can be held. C, as a language which assumes the programmer knows what (s)he is doing, will not check for overflow for you, and will give results which are plain wrong arithmetically if you exceed the limits.
There's an example [here]
from yesterday's C course, where I attempted to fill an array with an exponentially growing series of numbers, and ended up bursting even the capability of a long int
. You'll note that (on my machine, in this case), I ended up getting zeros back rather than the largest number the machine can handle - a dramatic failure of my code.
There's a header file - limit.h
- which #defines a whole load of constants such as INT_MAX to help you program to check for limits. There's an example of it in use [here]
in a training example from our C Programming course
(written 2012-01-25, updated 2012-01-28)
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articlesC201 - C and C based languages - C Language Fundamentals 
Turning C from source to a running program - (2006-10-06) 
Compiling C programs with gcc - an overview - (2008-06-10) 
Variables and pointers and references - C and C++ - (2009-01-23) 
What does const mean? C and C++ - (2010-01-15) 
Staring a C course with Hello World - why? - (2010-06-30) 
Learning to write good programs in C and C++ - separating out repeated code - (2011-01-04) 
Your program - you just provide the filling in the sandwich - (2011-04-08) 
Do I need to initialise variables - programming in C, C++, Perl, PHP, Python, Ruby or Java. - (2011-05-05) 
BODMAS - the order a computer evaluates arithmetic expressions - (2012-11-09) 
Learning to program - variables and constants - (2014-11-22) 
Preprocessor directives in C and C++ - what they mean - (2015-10-27) 
C - why is slow to write and debug) but fast to run? - (2015-11-01)
Some other Articles
Looking upBack to UniChars, char arrays and strings in C. Some early cautions and pitfalls.Are we one man, one vote? No, and we never have been. Integer types, and integer overflows, in CDefining, declaring and initialising variables in CPromoting a single one of your domains on the search enginesLearning about how to help people learning - and retaining C++ Courses - do I get official certification at the end of my Well House course?Emergency First Aid Provision at Well House Manor - part of the service
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