K&R is not intended to be a complete manual for every function in the C library: that's what man pages are for. K&R is a tutorial that introduces the C language (that is, the things that compilers deal with -- keywords, data types, syntax, ...), and shows some ways they can be connected together to make working programs. There are countless libraries that C can call: X-windows graphic libraries, and encryption libraries, and database access libraries, and networking libraries. They all come with their own manual pages. If the C Language book covered all those, then (a) you would not be able to lift it, and (b) it would be permanently out of date, as things evolve. My K&R is a First Edition from 1978, so the page numbering is not going to be the same as yours -- I'm not sure the section numbering will even be the same. That's why you use your own volume's index. Section 7.4 "Formatted Input" in mine covers scanf, 7.5 for sscanf, and 7.6 for fscanf. They are very similar, and use the same format "conversion specification" options: scanf reads from stdin, fscanf reads from a file, and sscanf reads from a string in memory. They work best for input where you are not too fussed about how it fits into input lines, so they are quite sloppy about whitespace. getline appears in section 1.9, as an example of how to write a function in C, and again in section 4.1 which is about how to structure a larger program. At the time, there was no standard library function getline(). When this was added into a library later, it was made to do the same kind of thing, but allows for expanding the input length automatically. So getline() reads a whole line from a file (which can be stdin or any other file or device), but it does not unpack any fields or values itself: there are a whole family of other functions that deal with those things. Some of those functions have names like strtok, strtol, strtod, and they all have man pages. Usually, there is a "See Also" section that links you into similar or related functions. fgets() is in section 7.8 "Line Input and Output" along with fputs(). fgets() is like getline, but simpler: you provide space for the string, but if it is too short you don't get a whole line of data, and you have to deal with that problem yourself. gets() is like fgets() but for stdin only. Also, it does not care at all about the space you provided for the input, and so can be misused to corrupt your program. The first four words in the man page are "Never use this function". All the code sections you posted are wrong, and here's why. char name[100000000]; reserves a buffer of 100 million characters as a local (on-stack) variable. That will use up all your stack and more besides, and your program won't run (probably not even load). char *x; would create a pointer to some chars, but it is not initialised to point to anywhere -- it is a pointer to something that does not exist. char **x; is even worse: is is a pointer to a pointer that does not exist, that would point to some chars that don't exist either. string x; uses a type "string" that does not exist in C. Some CS50 courses provide a header file that fixes up stuff like "string" to make your code easier to write, but they are not proper C and they hide the actual details, which is a piss-poor way to learn. scanf ("%c") reads exactly one character from the input. That is not a string. scanf ("%s") reads a string (like a name) from the input. It reads a real word: it skips any preceding whitespace, and it then only fetches text up to the next whitespace. Also, second example says #inclue and misses a ; off the scanf line, third one says scacnf, fourth one misses ; off scanf and a closing } . Compilers don't allow for carelessness. "string" is not part of the C language. It is verbal shorthand for "A row of text characters that ends with a zero (ASCII NUL) character. A row of things in C is usually called an array. To read and show a name in C, this would be good: #include int main(void) { char name [84]; //.. Allowing space for NUL terminator. printf("What's your name?\n"); scanf("%80s", name); //.. Limit field width on read. printf ("Good to meet you, %s!\n", name); } OK, I've spent 75 minutes writing this up. You need to do some work now. K&R is quite readable -- worth skimming the whole thing just to get an idea of what is in there -- get the shape of the language and fill in the detail later. Those dumb tutorials you found are mainly written for vanity by people who don't understand C themselves. 80% of it is junk. It really is worth reading enough man pages to understand why the information is presented like they do. More on reddit.com

First: C has no type for strings. It does not, simply out, have strings. Print functions expect a sequence of contiguous chars with a null (0x00) at the end. The same for strings length and other “string” functions. Second: the two first sentences do the same, they declare a variable as a pointer to a sequence of chars and in the same line it assigns a constant value where each element is one of the chars of the string and add a 0 at the end. So you can do string1[4] and string2[3]. Primitive value array pointers can be seen as an array or as a pointer indistinctly More on reddit.com

First, you should realize that the caesar and vigenere problems don't require you to create an encrypted string for later printing. You can print the result of encrypting each character as you go. Your declaration of c_txt is trying to create an array of i strings. What you could do is compute the length (call it p_len, for example) of the p_txt string, and then define an array whose element type is char and whose dimension is p_len + 1. The extra element is to allow for a null character ('\0') after the encrypted string. That null terminating character is needed if you intend to print the string using printf. More on reddit.com

You only need to free() data which is dynamically allocated using something like malloc() or mmap(). If you give a constant size like you said, either the data is statically allocated by the compiler in the .data segment (this is what happens if it's global or a static local variable) or it is allocated on the stack (regular local variables). In the former case, it lasts the whole program because that's the point. In the latter case, the memory is freed automatically for you when the function returns and the local variable leaves scope. More on reddit.com