#include <stdio.h>
 
int main(void)
{
    int a, b, c;
    // once you declare the variable, it is assigned a fixed memory location
    printf("a at %d  b at %d c at %d\n", &a, &b, &c); // // a at 1245060  b at 1245056 c at 1245052
 
    // initializes a, b and c to integer 3
    a = b = c = 3;
 
    printf("a = %d  b = %d  c = %d\n", a, b, c);  // a = 3  b = 3  c = 3
    printf("a at %d  b at %d c at %d\n", &a, &b, &c);  // a at 1245060  b at 1245056 c at 1245052
 
    a = 4;
    printf("a = %d  b = %d  c = %d\n", a, b, c);  // a = 4  b = 3  c = 3
    // 'a' has changed, but it's address has not
    printf("a at %d  b at %d c at %d\n", &a, &b, &c);  // a at 1245060  b at 1245056 c at 1245052
 
    a++;  // same as a = a + 1;  or  a += 1;
    printf("a = %d\n", a);  // a = 5
 
    // the time honored way to swap two variables using a temporary variable
    a = 77;
    b = 99;
    printf("before swap: a = %d  b = %d\n", a, b);
    c = b;  // here c is the temporary variable
    b = a;
    a = c;
    printf("after swap:  a = %d  b = %d\n", a, b);
 
    // exceeding the integer limits ...
    c = 2147483647 + 0;
    printf("2147483647 + 0 = %d\n", c);  // 2147483647
    c = 2147483647 + 1;
    // erroneous results
    printf("2147483647 + 1 = %d\n", c);  // -2147483648  ?
    c = 2147483647 * 3;
    printf("2147483647 * 3 = %d\n", c);  // 2147483645  ?
 
    getchar();  // console wait
    return 0;
}

# in Python you don't have to declare the variables
# Python gets the needed information during the initialization of the variables
# a, b, c all point to integer object 3
a = b = c = 3
 
print "a = %d  b = %d  c = %d" % (a, b, c)  # a = 3  b = 3  c = 3
print "a at %d  b at %d c at %d" % (id(a), id(b), id(c))  # a at 9721064  b at 9721064 c at 9721064
 
a = 4
print "a = %d  b = %d  c = %d" % (a, b, c)  # a = 4  b = 3  c = 3
# address pointed to by 'a' has changed, the object there is 4
print "a at %d  b at %d c at %d" % (id(a), id(b), id(c))  # a at 9721052  b at 9721064 c at 9721064
 
# a++ would increment the address and doesn't make much sense
# this construct is not allowed in Python
# however a = a + 1  or  a += 1 increments the integer object
a += 1
print "a = %d" % a   # a = 5
 
# swap two variables
a = 77
b = 99
print "before swap: a = %d  b = %d" % (a, b)
# swap, no temporary variable is needed
a, b = b, a
print "after swap:  a = %d  b = %d" % (a, b)
 
# exceeding the 32bit integer object
c = 2147483647 + 0
print "2147483647 + 0 = %d  type = %s" % (c, type(c))  # 2147483647  type = <type 'int'>
c = 2147483647 + 1
# no erroneous result
# simply switches type 32bit int to memory limited long
print "2147483647 + 1 = %d  type = %s" % (c, type(c))  # 2147483648  type = <type 'long'>
c = 2147483647 * 3
print "2147483647 * 3 = %d  type = %s" % (c, type(c))  # 6442450941  type = <type 'long'>
 
print
 
# a little extra information Python can easily give you ...
print "show a dictionary representing the current global symbol table:"
print globals()
 
raw_input()  # console wait