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Added missing information about scanf
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Yash
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@ -2,15 +2,15 @@
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language: C
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filename: learnc.c
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contributors:
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- ["Adam Bard", "http://adambard.com/"]
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- ["Árpád Goretity", "http://twitter.com/H2CO3_iOS"]
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- ["Jakub Trzebiatowski", "http://cbs.stgn.pl"]
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- ["Marco Scannadinari", "https://marcoms.github.io"]
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- ["Zachary Ferguson", "https://github.io/zfergus2"]
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- ["himanshu", "https://github.com/himanshu81494"]
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- ["Joshua Li", "https://github.com/JoshuaRLi"]
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- ["Dragos B. Chirila", "https://github.com/dchirila"]
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- ["Heitor P. de Bittencourt", "https://github.com/heitorPB/"]
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- ["Adam Bard", "http://adambard.com/"]
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- ["Árpád Goretity", "http://twitter.com/H2CO3_iOS"]
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- ["Jakub Trzebiatowski", "http://cbs.stgn.pl"]
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- ["Marco Scannadinari", "https://marcoms.github.io"]
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- ["Zachary Ferguson", "https://github.io/zfergus2"]
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- ["himanshu", "https://github.com/himanshu81494"]
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- ["Joshua Li", "https://github.com/JoshuaRLi"]
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- ["Dragos B. Chirila", "https://github.com/dchirila"]
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- ["Heitor P. de Bittencourt", "https://github.com/heitorPB/"]
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---
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Ah, C. Still **the** language of modern high-performance computing.
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@ -101,6 +101,12 @@ int main (int argc, char** argv)
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// %d is an integer, \n is a newline
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printf("%d\n", 0); // => Prints 0
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// take input using scanf
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// '&' is used to define the location
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// where we want to store the input value
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int input;
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scanf("%d", &input);
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///////////////////////////////////////
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// Types
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///////////////////////////////////////
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@ -118,7 +124,7 @@ int main (int argc, char** argv)
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// shorts are usually 2 bytes (use the `sizeof` operator to check)
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short x_short = 0;
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// chars are defined as the smallest addressable unit for a processor.
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// chars are defined as the smallest addressable unit for a processor.
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// This is usually 1 byte, but for some systems it can be more (ex. for TMS320 from TI it's 2 bytes).
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char x_char = 0;
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char y_char = 'y'; // Char literals are quoted with ''
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@ -167,19 +173,19 @@ int main (int argc, char** argv)
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// where the "{0}" part is called an "array initializer".
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// All elements (if any) past the ones in the initializer are initialized to 0:
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int my_array[5] = {1, 2};
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// So my_array now has five elements, all but the first two of which are 0:
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// So my_array now has five elements, all but the first two of which are 0:
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// [1, 2, 0, 0, 0]
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// NOTE that you get away without explicitly declaring the size
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// NOTE that you get away without explicitly declaring the size
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// of the array IF you initialize the array on the same line:
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int my_array[] = {0};
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// NOTE that, when not declaring the size, the size of the array is the number
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// NOTE that, when not declaring the size, the size of the array is the number
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// of elements in the initializer. With "{0}", my_array is now of size one: [0]
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// To evaluate the size of the array at run-time, divide its byte size by the
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// byte size of its element type:
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size_t my_array_size = sizeof(my_array) / sizeof(my_array[0]);
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// WARNING You should evaluate the size *before* you begin passing the array
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// to functions (see later discussion) because arrays get "downgraded" to
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// raw pointers when they are passed to functions (so the statement above
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// WARNING You should evaluate the size *before* you begin passing the array
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// to functions (see later discussion) because arrays get "downgraded" to
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// raw pointers when they are passed to functions (so the statement above
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// will produce the wrong result inside the function).
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// Indexing an array is like other languages -- or,
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@ -247,11 +253,11 @@ int main (int argc, char** argv)
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(float)i1 / i2; // => 0.5f
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i1 / (double)i2; // => 0.5 // Same with double
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f1 / f2; // => 0.5, plus or minus epsilon
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// Floating-point numbers are defined by IEEE 754, thus cannot store perfectly
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// exact values. For instance, the following does not produce expected results
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// because 0.1 might actually be 0.099999999999 insided the computer, and 0.3
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// might be stored as 0.300000000001.
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// exact values. For instance, the following does not produce expected results
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// because 0.1 might actually be 0.099999999999 insided the computer, and 0.3
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// might be stored as 0.300000000001.
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(0.1 + 0.1 + 0.1) != 0.3; // => 1 (true)
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// and it is NOT associative due to reasons mentioned above.
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1 + (1e123 - 1e123) != (1 + 1e123) - 1e123; // => 1 (true)
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@ -262,7 +268,7 @@ int main (int argc, char** argv)
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// eventually calls C which uses IEEE 754. It is mentioned this way not to
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// indicate that this is a poor implementation, but instead as a warning
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// that when doing floating point comparisons, a little bit of error (epsilon)
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// needs to be considered.
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// needs to be considered.
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// Modulo is there as well, but be careful if arguments are negative
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11 % 3; // => 2 as 11 = 2 + 3*x (x=3)
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@ -411,7 +417,7 @@ int main (int argc, char** argv)
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*/
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/*
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it is generally considered bad practice to do so, except if
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you really know what you are doing. See
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you really know what you are doing. See
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https://en.wikipedia.org/wiki/Spaghetti_code#Meaning
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*/
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@ -424,7 +430,7 @@ int main (int argc, char** argv)
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int x_hex = 0x01; // You can assign vars with hex literals
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// binary is not in the standard, but allowed by some
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// compilers (x_bin = 0b0010010110)
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// compilers (x_bin = 0b0010010110)
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// Casting between types will attempt to preserve their numeric values
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printf("%d\n", x_hex); // => Prints 1
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@ -626,7 +632,7 @@ printf("first: %d\nsecond: %d\n", first, second);
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// values will be swapped
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*/
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// Return multiple values.
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// Return multiple values.
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// C does not allow for returning multiple values with the return statement. If
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// you would like to return multiple values, then the caller must pass in the
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// variables where they would like the returned values to go. These variables must
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@ -637,9 +643,9 @@ int return_multiple( int *array_of_3, int *ret1, int *ret2, int *ret3)
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return 0; //return error code (false)
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//de-reference the pointer so we modify its value
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*ret1 = array_of_3[0];
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*ret2 = array_of_3[1];
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*ret3 = array_of_3[2];
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*ret1 = array_of_3[0];
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*ret2 = array_of_3[1];
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*ret3 = array_of_3[2];
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return 1; //return error code (true)
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}
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@ -901,10 +907,11 @@ Node createLinkedList(int *vals, int len);
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#endif /* End of the if precompiler directive. */
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```
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## Further Reading
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Best to find yourself a copy of [K&R, aka "The C Programming Language"](https://en.wikipedia.org/wiki/The_C_Programming_Language)
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It is *the* book about C, written by Dennis Ritchie, the creator of C, and Brian Kernighan. Be careful, though - it's ancient and it contains some
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It is _the_ book about C, written by Dennis Ritchie, the creator of C, and Brian Kernighan. Be careful, though - it's ancient and it contains some
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inaccuracies (well, ideas that are not considered good anymore) or now-changed practices.
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Another good resource is [Learn C The Hard Way](http://learncodethehardway.org/c/) (not free).
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