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Standard Library Functions

The prototypes for the some common functions in the C++ standard library are listed below. These prototypes and the functions definitions are declared within the std namespace. To access one of these functions, we #include its parent header file and either expose the entire namespace (using namespace std;) or add the std:: prefix to the function identifier.

C Library​

<cstdio> - Standard and File Input Output​

  • int scanf(const char* format, ...): Read data from standard input
  • int printf(const char* format, ...): Send data to standard output
  • int fscanf(FILE* stream, const char* format, ...): Read data from a file stream
  • int fprintf(FILE* stream, const char* format, ...): Send data to a file stream

<cstring> - C-Style Null-Terminated Strings​

  • size_t: Non-negative integer type
  • size_t strlen(const char* str): The number of characters in a C-style null-terminated string
  • char* strcpy(char* destination, const char* source): Copy C-style null-terminated string from source address to destination address
  • char* strcat(char* destination, const char* source): Concatenate C-style null-terminated string from source address to the string at the destination address
  • int strcmp(const char* str1, const char* str2): Compare C-style null-terminated strings at two addresses

<cstdlib> - General Utilities​

  • int abs(int i): Absolute value of i
  • int atoi(const char* str): Convert C-style null-terminated string (str) to an integer
  • int rand(): Generate a random number

<cmath> - Numerics​

  • double abs(double x): Absolute value of x
  • float abs(float x): Absolute value of x
  • double pow(double base, double exponent): Raises base to the power of exponent
  • double sqrt(double x): Square root of x

<cctype> - Character Handling​

  • int toupper(int c): Converts c to upper case
  • int tolower(int c): Converts c to lower case
  • int isupper(int c): Is c upper case?
  • int islower(int c): Is c lower case?
  • int isalpha(int c): Is c alphabetic?
  • int isdigit(int c): Is c a numeric digit?

Input Output Library​

<iostream> - Standard Input Output Objects​

  • streamsize: Integer type
  • fmtflags: Format flags type
  • char fill(char c): Set fill character to c
  • fmtflags setf(fmtflags f): Set format to f
  • fmtflags unsetf(fmtflags f): Unset format for f
  • streamsize width(streamsize w): Set field width to w
  • streamsize precision(streamsize p): Set floating-point precision to p
  • bool good() const: Good bit is set
  • bool eof() const: End of file bit is set
  • bool fail() const: Fail file bit is set
  • bool bad() const: Bad bit is set
  • bool eof() const: End of file bit is set
  • void clear(): Set error state to good

<iomanip> - Parametric Manipulators​

  • setfill(char c): Set fill character to c
  • setw(int w): Set field width to w
  • setprecision(int p): Set floating-point precision to p

<fstream> - File Input Output Objects​

  • void open(const char* f, ...): Open file named f and associate it with the current object
  • void close(): Close file associated with current object