printf()

Documentation info: int printf( const char *format [,argument] ...) 1

printf()

int printf( const char *format [,argument] ...) • • • • • Type of value returned ( int in this case) All functions return at most one value. The type void is used to indicate a function returns no value There is no requirement to use the value returned.

The printf() function returns the number of characters printed (including spaces); returns negative value if error occurs.

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printf()

int printf( const char *format [,argument] ...) • • Name of function; printf( ) in this case A function name is ALWAYS followed by a set of (), even if the function takes no arguments 3

printf()

int printf( const char *format [,argument] ...) • • • Type ( const char * ) and name ( format ) of first argument For the moment, const char * can be thought of as a series of characters enclosed in double quotes The name format may be thought of as a code indicating how the arguments are to be interpreted, and how the output should look.

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printf()

int printf( const char *format [,argument] ...) • • • zero of more optional arguments, each preceded by a comma zero because of the … optional because of the [ ] 5

examples - printf()

float a=67.49,b=9.999925; printf("hello %f there %f\n",a,b); printf("%f%f%f%f\n",a,a,b,b); printf("a=%f, b=%f",a,b); printf("Cool huh?\n"); Printed: hello 67.490000 there 9.999925

67.49900067.4990009.9999259.999925

a=67.490000, b=9.999925Cool huh?

Note: default %f prints as many digits as needed to represent the whole part of the value and exactly 6 digits to the right of the decimal point.

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examples - printf()

float a=67.49,b=9.999925; printf(" Price: █ %10f █ %10f \n",a,b); printf(" %8.2f

█ %8.4f

█ %5.1f

█ %7.5f

\n",a,a,b,b); printf(" a= %5.5f

, █ b= %0.2f

\n",a,b); Printed: 00000000011111111112222222222333333 print 12345678901234567890123456789012345 position Price: █ █67.499000

█ ██9.999925 columns ███67.49

█ █67.4900

█ █10.0

█ 9.99993 1 to 35 a= 67.49000

, █ b= 10.00

Note: On last line of output, the actual value was output; the printf routine overrode the specified width.

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examples - printf()

float a=67.49,b=9.999925; int i=184,j=-51; double x=123.456, y=-22.33; printf("%7.1lf%5d%8.2f\n",y,i,a); printf("%13.2f%4d%9.2lf\n",b,j,x); //changed Printed: 00000000011111111112222222222333333 print 12345678901234567890123456789012345 position -22.3 184 67.49 columns 10.00 -51 -22.33 1 to 35 Notes: d indicates decimal int eger f lf indicates float (that’s lower case L and f) indicates double (for double output, f OK too; not OK for input) 8

printf format specifications

General form: % [

flags

] [width] [.precision] [ { h | l | I64 | L } ] type flag meaning Left align the result within the given field

width

default Right align + Prefix the output value with a sign (+ or -) if the output value is of a Sign appears only for 0 signed type.

If

width

is prefixed with 0, zeros are added until the minimum

width

negative signed values (-) No padding (actually space is reached. If 0 and - appear, the 0 is ignored. padding) blankPrefix the output value with a blank if the output value is signed and No blank appears # # # positive; the blank is ignored if both the blank and + flags appear.

When used with the o, x, or X format, the # flag prefixes any nonzero output with 0, 0x, or 0X, respectively. Ignored when used with c, d, i, u, or s.

When used with the e, E, or f format, the # flag forces the output value to contain a decimal point in all cases.

When used with g or G format, forces the output value to contain a decimal point in all cases and prevents the truncation of trailing zeros.

No prefix Decimal point appears only if digits follow it.

Decimal point appears only if digits follow it. Trailing zeros are truncated.

This slide adapted from information in MSDN Library 9

printf format specifications

General form: % [flags] [

width

] [.precision] [ { h | l | I64 | L } ] type The

width

argument is a nonnegative decimal integer controlling the minimum number of characters printed. If the number of characters in the output value is less than the specified width, blanks are added to the left or the right of the values — depending on whether the –

flag

(for left alignment) is specified — until the minimum

width

is reached. • • Notes: If

width

is prefixed with 0, zeros are added until the minimum width is reached (not useful for left-aligned numbers).

The

width

specification never causes a value to be truncated. If the number of characters in the output value is greater than the specified width, or if

width

is not given, all characters of the value are printed (subject to the

precision

specification).

10 This slide adapted from information in MSDN Library

printf format specifications

General form: % [flags] [width] [.

precision

] [ { h | l | I64 | L } ] type typ meaning c The

precision

has no effect default character is printed d,i, The

precision

specifies the minimum number of digits to be printed. Default precision is 1.

u,o, If the number of digits in the argument is less than

precision

, the x,X output value is padded on the left with zeros. The value is not f truncated when the number of digits exceeds precision e,E The

precision

specifies the number of digits to be printed after the decimal point. The last printed digit is rounded.

Default precision is 6; if

precision

is 0 or the period The

precision

value specifies the number of digits after the decimal (.) appears without a point. If a decimal point appears, at least one digit appears before it. number following it, no The value is rounded to the appropriate number of digits.

g,GThe

precision

specifies the maximum number of significant digits printed.

decimal point is printed.

Six significant digits are printed, with any trailing zeros truncated.

s,S The

precision

specifies the maximum number of characters to be printed. Characters in excess of precision are not printed.

Characters are printed until a null character is encountered.

11 This slide adapted from information in MSDN Library

printf format specifications

General form: % [flags] [width] [.precision] [ {

h | l | I64 | L

} ] type

to specify

long, long int long unsigned int short int short unsigned int __int64 use prefix with type specifier l d, i, o, x, X l h u d, i, o, x, X h I64 u d, i, o, x, X Note: this is not a complete list.

Note: these prefixes are Microsoft extensions and not ANSI compatible 12 This slide adapted from information in MSDN Library

printf format specifications

General form: % [flags] [width] [.precision] [ { h | l | I64 | L } ]

type type

what c Single byte char d or i Signed decimal integer X or x o u Unsigned hexadecimal integer (using ABCDEF or abcdef) Unsigned octal integer Unsigned decimal integer f Signed real value having the form [-]xxxx.yyyy where yyyy is dependant upon the requested precision, and xxxx is dependent upon the requested width and/or magnitude of value e or E Signed real value of form [-]xxxx.yyyye

± zzz, where xxxx and g or G yyyy are as described for f; zzz is a three digit exponent. E is the same as e except a capital E is printed Automatically selects f or e/E based on the magnitude of the value s String - assumes start address given; terminates at \0 (null) Note: not a complete list

printf() examples

printf("vv% dww%-dxx%+dyy%dzz\n",-12,-34,-56,-78); ..../....1..../....2..../....3..../ <= ruler vv-12ww-34xx-56yy-78zz printf("vv% dww%-dxx%+dyy%dzz\n",12,34,56,78); ..../....1..../....2..../....3..../ <= ruler vv 12ww34xx+56yy78zz printf("vv% 5dww%-5dxx%+5dyy%5dzz\n",-12,-34,-56,-78); ..../....1..../....2..../....3..../ <= ruler vv -12ww-34 xx -56yy -78zz printf("vv% 5dww%-5dxx%+5dyy%5dzz\n",12,34,56,78); ..../....1..../....2..../....3..../ <= ruler vv 12ww34 xx +56yy 78zz 14

printf() examples

printf("v% 05dw%-05dx%+05dy%05dz\n",-12,-34,-56,-78); ..../....1..../....2..../....3..../ <= ruler v-0012w-34 x-0056y-0078z printf("v% 05dw%-05dx%+05dy%05dz\n",12,34,56,78); ..../....1..../....2..../....3..../ <= ruler v 0012w34 x+0056y00078z printf("v%7.3dw% 7.3dx%-7.3dy%+7.3dz\n",-12,-34,-56,-78); ..../....1..../....2..../....3..../ <= ruler v -012w -034x-056 y -078z print("v%7.3dw% 7.3dx%-7.3dy%+7.3dz\n", 12, 34, 56, 78); ..../....1..../....2..../....3..../ <= ruler v 012w 034x056 y +078z 15

printf() examples

printf("w%7.2fx%7.2fy%7.2fz\n",-1.234,-3.456,-5.6); ..../....1..../....2..../....3..../ <= ruler w -1.23x -3.46y -5.60z

printf("w%7.2fx%7.2fy%7.2fz\n", 1.234, 3.456, 5.6); ..../....1..../....2..../....3..../ <= ruler w 1.23w 3.46y 5.60z

printf("w%7.2fx%7.2f\n",-1234567.8,1234567.8); ..../....1..../....2..../....3..../ <= ruler w-1234567.8x1234567.8z

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