如果你安裝的Visual Studio，以及它的Visual C++的話，
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那么在安裝目錄下的VC/crt/src下有所有標(biāo)準(zhǔn)C庫(kù)的源代碼
另外，h后綴的頭文件包含函數(shù)的聲明，具體的實(shí)現(xiàn)都在c后綴的源碼文件中
1）字符串操作
strcpy(p, p1) 復(fù)制字符串
strncpy(p, p1, n) 復(fù)制指定長(zhǎng)度字符串
strcat(p, p1) 附加字符串
strncat(p, p1, n) 附加指定長(zhǎng)度字符串
strlen(p) 取字符串長(zhǎng)度
strcmp(p, p1) 比較字符串
strcasecmp忽略大小寫比較字符串
strncmp(p, p1, n) 比較指定長(zhǎng)度字符串
strchr(p, c) 在字符串中查找指定字符
strrchr(p, c) 在字符串中反向查找
strstr(p, p1) 查找字符串
strpbrk(p, p1) 以目標(biāo)字符串的所有字符作為集合，在當(dāng)前字符串查找該集合的任一元素
strspn(p, p1) 以目標(biāo)字符串的所有字符作為集合，在當(dāng)前字符串查找不屬于該集合的任一元素的偏移
strcspn(p, p1) 以目標(biāo)字符串的所有字符作為集合，在當(dāng)前字符串查找屬于該集合的任一元素的偏移
* 具有指定長(zhǎng)度的字符串處理函數(shù)在已處理的字符串之后填補(bǔ)零結(jié)尾符
2）字符串到數(shù)值類型的轉(zhuǎn)換
strtod(p, ppend) 從字符串 p 中轉(zhuǎn)換 double 類型數(shù)值，并將后續(xù)的字符串指針存儲(chǔ)到 ppend 指向的 char* 類型存儲(chǔ)。
strtol(p, ppend, base) 從字符串 p 中轉(zhuǎn)換 long 類型整型數(shù)值，base 顯式設(shè)置轉(zhuǎn)換的整型進(jìn)制，設(shè)置為 0 以根據(jù)特定格式判斷所用進(jìn)制，0x, 0X 前綴以解釋為十六進(jìn)制格式整型，0 前綴以解釋為八進(jìn)制格式整型
atoi(p) 字符串轉(zhuǎn)換到 int 整型
atof(p) 字符串轉(zhuǎn)換到 double 符點(diǎn)數(shù)
atol(p) 字符串轉(zhuǎn)換到 long 整型
3）字符檢查
isalpha() 檢查是否為字母字符
isupper() 檢查是否為大寫字母字符
islower() 檢查是否為小寫字母字符
isdigit() 檢查是否為數(shù)字
isxdigit() 檢查是否為十六進(jìn)制數(shù)字表示的有效字符
isspace() 檢查是否為空格類型字符
iscntrl() 檢查是否為控制字符
ispunct() 檢查是否為標(biāo)點(diǎn)符號(hào)
isalnum() 檢查是否為字母和數(shù)字
isprint() 檢查是否是可打印字符
isgraph() 檢查是否是圖形字符，等效于 isalnum() | ispunct()
很遺憾,標(biāo)準(zhǔn)庫(kù)中的函數(shù)結(jié)合了系統(tǒng),硬件等的綜合能力,是比較近機(jī)器的功能實(shí)現(xiàn),所以大部分是用匯編完成的,而且已經(jīng)導(dǎo)入到了lib和dll里了,就是說,他們已經(jīng)被編譯好了,似乎沒有代碼的存在了.
能看到的也只有dll中有多少函數(shù)被共享.
第三方可能都是dll,因?yàn)樯厦嬉舱f了,dll是編譯好的,只能看到成品,就可以隱藏代碼,保護(hù)自己的知識(shí)產(chǎn)權(quán),同時(shí)也是病毒的歸宿...... 當(dāng)然,除了DLL的確還存在一種東西,插件程序~~~
C語(yǔ)言標(biāo)準(zhǔn)庫(kù)函數(shù)
標(biāo)準(zhǔn)io函數(shù)
Standard C I/O
clearerr() clears errors
fclose() close a file
feof() true if at the end-of-file
ferror() checks for a file error
fflush() writes the contents of the output buffer
fgetc() get a character from a stream
fgetpos() get the file position indicator
fgets() get a string of characters from a stream
fopen() open a file
fprintf() print formatted output to a file
fputc() write a character to a file
fputs() write a string to a file
fread() read from a file
freopen() open an existing stream with a different name
fscanf() read formatted input from a file
fseek() move to a specific location in a file
fsetpos() move to a specific location in a file
ftell() returns the current file position indicator
fwrite() write to a file
getc() read a character from a file
getchar() read a character from STDIN
gets() read a string from STDIN
perror() displays a string version of the current error to STDERR
printf() write formatted output to STDOUT
putc() write a character to a stream
putchar() write a character to STDOUT
puts() write a string to STDOUT
remove() erase a file
rename() rename a file
rewind() move the file position indicator to the beginning of a file
scanf() read formatted input from STDIN
setbuf() set the buffer for a specific stream
setvbuf() set the buffer and size for a specific stream
sprintf() write formatted output to a buffer
sscanf() read formatted input from a buffer
tmpfile() return a pointer to a temporary file
tmpnam() return a unique filename
ungetc() puts a character back into a stream
vprintf, vfprintf, vsprintf write formatted output with variable argument lists
標(biāo)準(zhǔn)字符/字符串處理函數(shù)
atof() converts a string to a double
atoi() converts a string to an integer
atol() converts a string to a long
isalnum() true if alphanumeric
isalpha() true if alphabetic
iscntrl() true if control character
isdigit() true if digit
isgraph() true if a graphical character
islower() true if lowercase
isprint() true if a printing character
ispunct() true if punctuation
isspace() true if space
isupper() true if uppercase character
isxdigit() true if a hexidecimal character
memchr() searches an array for the first occurance of a character
memcmp() compares two buffers
memcpy() copies one buffer to another
memmove() moves one buffer to another
memset() fills a buffer with a character
strcat() concatenates two strings
strchr() finds the first occurance of a character in a string
strcmp() compares two strings
strcoll() compares two strings in accordance to the current locale
strcpy() copies one string to another
strcspn() searches one string for any characters in another
strerror() returns a text version of a given error code
strlen() returns the length of a given string
strncat() concatenates a certain amount of characters of two strings
strncmp() compares a certain amount of characters of two strings
strncpy() copies a certain amount of characters from one string to another
strpbrk() finds the first location of any character in one string, in another string
strrchr() finds the last occurance of a character in a string
strspn() returns the length of a substring of characters of a string
strstr() finds the first occurance of a substring of characters
strtod() converts a string to a double
strtok() finds the next token in a string
strtol() converts a string to a long
strtoul() converts a string to an unsigned long
strxfrm() converts a substring so that it can be used by string comparison functions
tolower() converts a character to lowercase
toupper() converts a character to uppercase
標(biāo)準(zhǔn)數(shù)學(xué)函數(shù)
abs() absolute value
acos() arc cosine
asin() arc sine
atan() arc tangent
atan2() arc tangent, using signs to determine quadrants
ceil() the smallest integer not less than a certain value
cos() cosine
cosh() hyperbolic cosine
div() returns the quotient and remainder of a division
exp() returns "e" raised to a given power
fabs() absolute value for floating-point numbers
floor() returns the largest integer not greater than a given value
fmod() returns the remainder of a division
frexp() decomposes a number into scientific notation
labs() absolute value for long integers
ldexp() computes a number in scientific notation
ldiv() returns the quotient and remainder of a division, in long integer form
log() natural logarithm
log10() natural logarithm, in base 10
modf() decomposes a number into integer and fractional parts
pow() returns a given number raised to another number
sin() sine
sinh() hyperbolic sine
sqrt() square root
tan() tangent
tanh() hyperbolic tangent
標(biāo)準(zhǔn)時(shí)間/日期函數(shù)
asctime() a textual version of the time
clock() returns the amount of time that the program has been running
ctime() returns a specifically formatted version of the time
difftime() the difference between two times
gmtime() returns a pointer to the current Greenwich Mean Time
localtime() returns a pointer to the current time
mktime() returns the calendar version of a given time
strftime() returns individual elements of the date and time
time() returns the current calendar time of the system
標(biāo)準(zhǔn)內(nèi)存管理函數(shù)
calloc() allocates a two-dimensional chunk of memory
free() makes memory available for future allocation
malloc() allocates memory
realloc() changes the size of previously allocated memory
其它標(biāo)準(zhǔn)函數(shù)
abort() stops the program
assert() stops the program if an expression isn';t true
atexit() sets a function to be called when the program exits
bsearch() perform a binary search
exit() stop the program
getenv() get enviornment information about a variable
longjmp() start execution at a certain point in the program
qsort() perform a quicksort
raise() send a signal to the program
rand() returns a pseudorandom number
setjmp() set execution to start at a certain point
signal() register a function as a signal handler
srand() initialize the random number generator
system() perform a system call
va_arg() use variable length parameter lists
標(biāo)準(zhǔn)庫(kù)只是定義接口，具體怎么實(shí)現(xiàn)就得看操作系統(tǒng)，你說win下和linux下這些函數(shù)的實(shí)現(xiàn)會(huì)一樣嗎。當(dāng)然不一樣，看這些學(xué)源碼，不如看看c標(biāo)準(zhǔn)，c89或c99.
那可以看內(nèi)核，看系統(tǒng)調(diào)用是怎么樣實(shí)現(xiàn)的，你說的那些都是基于系統(tǒng)調(diào)用的
你說的就是庫(kù)函數(shù)的源碼，也就是glibc，源碼在可以下到，比如下載，打開后就可以看到你需要的各種庫(kù)的具體實(shí)現(xiàn)代碼，比如在string中的strcat.c中就有
char?*strcat?(dest,?src)
char?*dest;
const?char?*src;
{
char?*s1?=?dest;
const?char?*s2?=?src;
reg_char?c;
/*?Find?the?end?of?the?string.??*/
do
c?=?*s1++;
while?(c?!=?'\0');
/*?Make?S1?point?before?the?next?character,?so?we?can?increment
it?while?memory?is?read?(wins?on?pipelined?cpus).??*/
s1?-=?2;
do
{
c?=?*s2++;
*++s1?=?c;
}
while?(c?!=?'\0');
return?dest;
}
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