When %d format specifier is used with a char variable, it prints the ASCII value. The ASCII value of 'A' is 65. If it were 'a', the value would be 97.

malloc() (memory allocation) is the standard function in C for dynamic memory allocation. It returns a void pointer to the allocated memory. The syntax is: ptr = (type*)malloc(size);

Array indexing in C starts from 0. str[0]='H', str[1]='e', str[2]='l', str[3]='l', str[4]='o', str[5]='\0'. Therefore, str[1] is 'e'.

strcmp() is the standard library function used to compare two strings. It returns 0 if strings are equal, negative if first string is less, and positive if first string is greater. It's declared in string.h.

p is a pointer to x, so &x gives the address of x. *p (dereferencing) gives the value stored at that address, which is 5. The output will be 5.

The operator += means x = x + 3. So x = 5 + 3 = 8. The printf statement outputs 8.

The do-while loop executes the loop body at least once before checking the condition. Other loops check the condition before execution. Syntax: do { } while(condition);

The pre-increment operator (++x) increments x first, then assigns it. So x becomes 6, and y is assigned 6. Output: 6 6.

malloc() (memory allocation) is used to dynamically allocate memory on the heap in C. It requires #include <stdlib.h>. new() is used in C++, not C.

This is a swap operation. Initially a=10, b=20. After temp=a (temp=10), a=b (a=20), b=temp (b=10). Output: 20 10.