1. More on Numerical Computation CS-2301 B-term 20081 More on Numerical Computation CS-2301, System Programming for Non-majors (Slides include materials from The C Programming Language, 2 nd ed., by Kernighan and Ritchie and from C: How to Program, 5 th ed., by Deitel and Deitel)

2. More on Numerical Computation CS-2301 B-term 20082 Reading Assignment Chapter 2 of Kernighan & Ritchie

3. More on Numerical Computation CS-2301 B-term 20083 Digression on scanf() & printf() Prints a string in which each conversion specifier is replaced with value of corresponding argument printf(“string in double quotes”, arg1, arg2, arg3, …); Conversion specifier:– Begins with ‘%’ character Describes how to print one argument ith conversion specifier in string says how to print arg i Resulting string printed on stdout Returns number of characters printed

4. More on Numerical Computation CS-2301 B-term 20084 printf() (continued) %d, %i — decimal number %u — unsigned decimal number %c — character %s — string %f — floating point number e.g., 3.14159 %e, E — floating point number e.g., 2.9979e+8 or 2.9979E+8 % — a single ‘%’ character See textbook for full list (pp 154, 244)

5. More on Numerical Computation CS-2301 B-term 20085 printf() Optional Controls %6.4d ^ – minimum field width Padded on left ^ – precision of number %.12s ^ – width of string %-6.4d ^ – indicates left justify Padded on right

6. More on Numerical Computation CS-2301 B-term 20086 printf() Examples int j = 24; float twoPi = 2 * pi; printf(“j=%d, k=%f\n”, j, twoPi ); Output j=24, k=6.28319 printf(“%4d %4d %4d %6d”, 1, 10, 100, 1000); Output 1 10 100 1000......

7. More on Numerical Computation CS-2301 B-term 20087 scanf() Reads input, decomposes into individual variables Opposite of printf() scanf(“string in double quotes”, &arg1, &arg2, &arg3, …); Arguments must be locations – use‘ & ’ Converts input string according to scan string, stores in variables Returns number of matched and stored items –Or EOF if end of file is encountered Stops at end of string or when no match is found

8. More on Numerical Computation CS-2301 B-term 20088 scanf() Examples int i; double x; char c; scanf(“%d%f%c”, &i, &x, &c); Looks first for an integer Skips white space Looks next for a floating point Skips white space Looks next for a single character Does not skip white space; returns the first character it finds

9. More on Numerical Computation CS-2301 B-term 20089 scanf() Formats %d — any decimal number %u — an unsigned integer %c — character White space not skipped %e, f, g — floating point number %s — string Defer to later in the course % — matches a single ‘%’ character Any other character Matches that character

10. More on Numerical Computation CS-2301 B-term 200810 scanf() Formats %d — any decimal number %u — an unsigned integer %c — character White space not skipped %e, f, g — floating point number %s — string Defer to later in the course % — matches a single ‘%’ character Any other character Matches that character May specify “ h ” or “ l ” indicating short or long integer, float vs. double

11. More on Numerical Computation CS-2301 B-term 200811 Questions?

12. More on Numerical Computation CS-2301 B-term 200812 More Numerical Operators Relational operators –, >=, ==, != –Return 0 if false, 1 if true Let int a = 3; Then a = 3 returns 1 a == 3 returns 1 a != 3 returns 0

13. More on Numerical Computation CS-2301 B-term 200813 More Numerical Operators Relational operators –, >=, ==, != –Return 0 if false, 1 if true Let int a = 3; Then a = 3 returns 1 a == 3 returns 1 a != 3 returns 0 Relational operators are not special in C. They are just like any other operators in expressions

14. More on Numerical Computation CS-2301 B-term 200814 Precedence of Relational Operators Comparisons: less than arithmetic operators Equality & inequality: less than comparisons See p.53 Examples i < lim -1 means i < (lim – 1) X + (y >= 3) returns the value X (when y = 3 )

15. More on Numerical Computation CS-2301 B-term 200815 Increment & Decrement Operators ++x, --x, x++, x-- Increments or decrements x by 1 ++x – increments x, returns new value of x x++ – increments x, returns old value of x Used in many situations, especially for loops --x – decrements x, returns new value of x x-- – decrements x, returns old value of x High precedence than *, /, % –Associates right to left

16. More on Numerical Computation CS-2301 B-term 200816 Bitwise Operations & – bitwise AND | – bitwise OR (inclusive) ^ – bitwise exclusive OR << – left shift Same as multiplying by 2 (i.e., fills low-order bits with zeros) >> – right shift Machine dependent fill on left ~ – one’s complement May only be applied to integral types i.e., int, short, long, char signed or unsigned

17. More on Numerical Computation CS-2301 B-term 200817 Conditional Expressions expr 1 ? expr 2 : expr 3 –Evaluate expr 1. –If result is true, return expr 2 –Otherwise return expr 3 Example, –z = (a < b) ? a : b –Assigns z the value of a if a < b, or b otherwise See tricky code at end of §2.11 –For use in Homework #1

18. More on Numerical Computation CS-2301 B-term 200818 Assignment Operator (yet again) location += expression means –Add expression to the value at location and assign the result back into location Similarly for -=, *=, /=, %=, ^=. |=, >= E.g., x *= a is the same as x = x * a y /= b is the same as y = y * b z <<= 3 is the same as z = z << 3

19. More on Numerical Computation CS-2301 B-term 200819 Type Conversion May be automatic or explicit See §2.7 Automatic, for signed operands:– If either is long double, convert other to long double Else if either is double, convert other to double Else if either is float, convert other to float Otherwise, convert char and short to int and then if either is long, convert other to long I.e., “promote” numerical types from lower to higher

20. More on Numerical Computation CS-2301 B-term 200820 Type Conversion (continued) Automatic type conversion of unsigned integer values is Tricky and Machine dependent

21. More on Numerical Computation CS-2301 B-term 200821 Explicit Type Conversion Definition – cast A unary operator applied to an expression to explicitly force the value to a particular type Represented as (type) expression High precedence, equal to unary operators Associates right-to-left Example (int) sqrt(2*pi) Converts the square root of 2π to an integer

22. More on Numerical Computation CS-2301 B-term 200822 Questions? Read or review Chapter 2