C++ for Scientists - Technische Universität Dresden

C ++ Basics
Chapter 2
In this first chapter we will briefly introduce some basic knowledge about C ++. A useful site
with a reference manual to C ++ commands is http://www.cplusplus.com/.
2.1 Our First Program
As an introduction to the C ++ language, let us look at the following example:
#include
int main ()
{
std::cout ≪ ”Answer to the Ultimate Question of Life, the Universe, and Everything is ”
≪ 6 ∗ 7 ≪ std::endl;
return 0;
}
according to Douglas Adams’ “Hitchhiker’s Guide to the Galaxy.” This short example shows
already many things about C ++:
• The first line includes a file name “iostream.” Whatever is defined in this file will be
defined in our program as well. The file “iostream” contains the standard I/O of C ++.
Input and output is not part of the core language in C ++ but part of the standard libraries.
This means that we cannot program I/O commands without including “iostream” (or
something similar). But it also means that this file must exist in every compiler because
it is part of the standard. Include commands should be at the beginning of the file if
possible.
• the main program is called main and has an integer return value, which is set to 0 by the
return command. The caller of a program (usually the operating system) knows that it
finished successfully when a 0 is returned. A return code other than 0 symbolizes that
something went wrong and often the return code also says something about what went
wrong.
• Braces “{ }” denote a block/group of code (also called a compound statement). Variables
declared within “{ }” groups are only accessible within this block.
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