There is a quite old Unix editor called vi. To use vi to edit file foo. You are on your own to learn how to use this editor. Command man vi will show a manual on using vi.
An alternative is emacs. Emacs is a large, versatile and extensible text editor. It has many options, and you can create your own commands as well. You can also have several files open at once and run a terminal from within emacs, which is convenient for using ssh. To use emacs to edit file foo. To learn how to use emacs, see using emacs.
Typing a tab indents the current line. Also, when you type a right brace, it shows you the matching left brace, a feature that is very useful for keeping braces matching correctly. You should always ask the compiler to give you warnings. Rich Hunter September 4, , am. Hello again. Ramesh Natarajan September 4, , pm. Thanks a lot for pointing out the issue. Anonymous October 25, , pm. Raj January 16, , am. Balajilp March 15, , am. Ehan Chang April 5, , pm. Shrey Kaushal March 3, , pm.
Suman Dutta May 3, , am. The compiler can help us by optimizing the code, either for speed to run faster , or for space to occupy a smaller space , or some combination of the two. This also means the compilation will take longer, as the compiler tries to apply various optimization algorithms to the code. This optimization is supposed to be conservative, in that it ensures us the code will still perform the same functionality as it did when compiled without optimization well, unless there are bugs in our compiler.
Usually can define an optimization level by adding a number to the '-O' flag. The higher the number - the better optimized the resulting program will be, and the slower the compiler will complete the compilation. One should note that because optimization alters the code in various ways, as we increase the optimization level of the code, the chances are higher that an improper optimization will actually alter our code, as some of them tend to be non-conservative, or are simply rather complex, and contain bugs.
For example, for a long time it was known that using a compilation level higher than 2 or was it higher than 3? If you'll read your compiler's manual page, you'll soon notice that it supports an almost infinite number of command line options dealing with optimization.
Using them properly requires thorough understanding of compilation theory and source code optimization theory, or you might damage your resulting code.
A good compilation theory course preferably based on "the Dragon Book" by Aho, Sethi and Ulman could do you good. Normally the compiler only generates error messages about erroneous code that does not comply with the C standard, and warnings about things that usually tend to cause errors during runtime. However, we can usually instruct the compiler to give us even more warnings, which is useful to improve the quality of our source code, and to expose bugs that will really bug us later.
With gcc, this is done using the '-W' flag. However, it is better to eliminate the warnings than to eliminate the usage of this flag. Usually, this option will save us more time than it will cause us to waste, and if used consistently, we will get used to coding proper code without thinking too much about it.
One should also note that some code that works on some architecture with one compiler, might break if we use a different compiler, or a different system, to compile the code on. When developing on the first system, we'll never see these bugs, but when moving the code to a different platform, the bug will suddenly appear.
Also, in many cases we eventually will want to move the code to a new system, even if we had no such intentions initially. Note that sometimes '-Wall' will give you too many errors, and then you could try to use some less verbose warning level. Read the compiler's manual to learn about the various '-W' options, and use those that would give you the greatest benefit. Initially they might sound too strange to make any sense, but if you are or when you will become a more experienced programmer, you will learn which could be of good use to you.
So you learned how to compile a single-source program properly hopefully by now you played a little with the compiler and tried out a few examples of your own. Yet, sooner or later you'll see that having all the source in a single file is rather limiting, for several reasons: As the file grows, compilation time tends to grow, and for each little change, the whole program has to be re-compiled.
It is very hard, if not impossible, that several people will work on the same project together in this manner. Managing your code becomes harder. Backing out erroneous changes becomes nearly impossible.
There are two possible ways to compile a multi-source C program. The first is to use a single command line to compile all the files. Suppose that we have a program whose source is found in files "main. In fact it has a very specific order of directories in which it looks for executables.
If it does not find the executable in any of these it gives up its search. It may be that your shell is not set-up to look in your current directory. By typing. The shell searches these directories from left- to-right. The last directory searched is my current directory.
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