From 44e15f80047d0675c421c38aadb2a8dc09d32d06 Mon Sep 17 00:00:00 2001 From: Yash Date: Mon, 10 Oct 2022 22:27:35 +0530 Subject: Added missing information about scanf --- c.html.markdown | 63 ++++++++++++++++++++++++++++++++------------------------- 1 file changed, 35 insertions(+), 28 deletions(-) diff --git a/c.html.markdown b/c.html.markdown index a898f052..cd6b5ad2 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -2,15 +2,15 @@ language: C filename: learnc.c contributors: - - ["Adam Bard", "http://adambard.com/"] - - ["Árpád Goretity", "http://twitter.com/H2CO3_iOS"] - - ["Jakub Trzebiatowski", "http://cbs.stgn.pl"] - - ["Marco Scannadinari", "https://marcoms.github.io"] - - ["Zachary Ferguson", "https://github.io/zfergus2"] - - ["himanshu", "https://github.com/himanshu81494"] - - ["Joshua Li", "https://github.com/JoshuaRLi"] - - ["Dragos B. Chirila", "https://github.com/dchirila"] - - ["Heitor P. de Bittencourt", "https://github.com/heitorPB/"] + - ["Adam Bard", "http://adambard.com/"] + - ["Árpád Goretity", "http://twitter.com/H2CO3_iOS"] + - ["Jakub Trzebiatowski", "http://cbs.stgn.pl"] + - ["Marco Scannadinari", "https://marcoms.github.io"] + - ["Zachary Ferguson", "https://github.io/zfergus2"] + - ["himanshu", "https://github.com/himanshu81494"] + - ["Joshua Li", "https://github.com/JoshuaRLi"] + - ["Dragos B. Chirila", "https://github.com/dchirila"] + - ["Heitor P. de Bittencourt", "https://github.com/heitorPB/"] --- Ah, C. Still **the** language of modern high-performance computing. @@ -101,6 +101,12 @@ int main (int argc, char** argv) // %d is an integer, \n is a newline printf("%d\n", 0); // => Prints 0 + // take input using scanf + // '&' is used to define the location + // where we want to store the input value + int input; + scanf("%d", &input); + /////////////////////////////////////// // Types /////////////////////////////////////// @@ -118,7 +124,7 @@ int main (int argc, char** argv) // shorts are usually 2 bytes (use the `sizeof` operator to check) short x_short = 0; - // chars are defined as the smallest addressable unit for a processor. + // chars are defined as the smallest addressable unit for a processor. // This is usually 1 byte, but for some systems it can be more (ex. for TMS320 from TI it's 2 bytes). char x_char = 0; char y_char = 'y'; // Char literals are quoted with '' @@ -167,19 +173,19 @@ int main (int argc, char** argv) // where the "{0}" part is called an "array initializer". // All elements (if any) past the ones in the initializer are initialized to 0: int my_array[5] = {1, 2}; - // So my_array now has five elements, all but the first two of which are 0: + // So my_array now has five elements, all but the first two of which are 0: // [1, 2, 0, 0, 0] - // NOTE that you get away without explicitly declaring the size + // NOTE that you get away without explicitly declaring the size // of the array IF you initialize the array on the same line: int my_array[] = {0}; - // NOTE that, when not declaring the size, the size of the array is the number + // NOTE that, when not declaring the size, the size of the array is the number // of elements in the initializer. With "{0}", my_array is now of size one: [0] // To evaluate the size of the array at run-time, divide its byte size by the // byte size of its element type: size_t my_array_size = sizeof(my_array) / sizeof(my_array[0]); - // WARNING You should evaluate the size *before* you begin passing the array - // to functions (see later discussion) because arrays get "downgraded" to - // raw pointers when they are passed to functions (so the statement above + // WARNING You should evaluate the size *before* you begin passing the array + // to functions (see later discussion) because arrays get "downgraded" to + // raw pointers when they are passed to functions (so the statement above // will produce the wrong result inside the function). // Indexing an array is like other languages -- or, @@ -247,11 +253,11 @@ int main (int argc, char** argv) (float)i1 / i2; // => 0.5f i1 / (double)i2; // => 0.5 // Same with double f1 / f2; // => 0.5, plus or minus epsilon - + // Floating-point numbers are defined by IEEE 754, thus cannot store perfectly - // exact values. For instance, the following does not produce expected results - // because 0.1 might actually be 0.099999999999 insided the computer, and 0.3 - // might be stored as 0.300000000001. + // exact values. For instance, the following does not produce expected results + // because 0.1 might actually be 0.099999999999 insided the computer, and 0.3 + // might be stored as 0.300000000001. (0.1 + 0.1 + 0.1) != 0.3; // => 1 (true) // and it is NOT associative due to reasons mentioned above. 1 + (1e123 - 1e123) != (1 + 1e123) - 1e123; // => 1 (true) @@ -262,7 +268,7 @@ int main (int argc, char** argv) // eventually calls C which uses IEEE 754. It is mentioned this way not to // indicate that this is a poor implementation, but instead as a warning // that when doing floating point comparisons, a little bit of error (epsilon) - // needs to be considered. + // needs to be considered. // Modulo is there as well, but be careful if arguments are negative 11 % 3; // => 2 as 11 = 2 + 3*x (x=3) @@ -411,7 +417,7 @@ int main (int argc, char** argv) */ /* it is generally considered bad practice to do so, except if - you really know what you are doing. See + you really know what you are doing. See https://en.wikipedia.org/wiki/Spaghetti_code#Meaning */ @@ -424,7 +430,7 @@ int main (int argc, char** argv) int x_hex = 0x01; // You can assign vars with hex literals // binary is not in the standard, but allowed by some - // compilers (x_bin = 0b0010010110) + // compilers (x_bin = 0b0010010110) // Casting between types will attempt to preserve their numeric values printf("%d\n", x_hex); // => Prints 1 @@ -626,7 +632,7 @@ printf("first: %d\nsecond: %d\n", first, second); // values will be swapped */ -// Return multiple values. +// Return multiple values. // C does not allow for returning multiple values with the return statement. If // you would like to return multiple values, then the caller must pass in the // variables where they would like the returned values to go. These variables must @@ -637,9 +643,9 @@ int return_multiple( int *array_of_3, int *ret1, int *ret2, int *ret3) return 0; //return error code (false) //de-reference the pointer so we modify its value - *ret1 = array_of_3[0]; - *ret2 = array_of_3[1]; - *ret3 = array_of_3[2]; + *ret1 = array_of_3[0]; + *ret2 = array_of_3[1]; + *ret3 = array_of_3[2]; return 1; //return error code (true) } @@ -901,10 +907,11 @@ Node createLinkedList(int *vals, int len); #endif /* End of the if precompiler directive. */ ``` + ## Further Reading Best to find yourself a copy of [K&R, aka "The C Programming Language"](https://en.wikipedia.org/wiki/The_C_Programming_Language) -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 +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 inaccuracies (well, ideas that are not considered good anymore) or now-changed practices. Another good resource is [Learn C The Hard Way](http://learncodethehardway.org/c/) (not free). -- cgit v1.2.3