[Courses] C Programming For Absolute Beginners, Lesson 2: Fun With Printf, Scanf, Puts, and Variables

[Leslie]

re: C for Beginners, Lesson 2

Hi.
Before I get to the homework, a quick question:
I thought I would modify the 'age' program to input a string (name)
instead.
I guessed I should replace 'int age' with 'char name'.
So I wrote this:

/* 
name; an example program showing the difference between 
puts and printf 
*/ 

#include <stdio.h> 

int main() 
{ 
	char name; 

	puts( "Please enter your name: " ); 
	scanf( "%s", &name ); 
	printf( "Hi, %s.\n", name); 

	return 0; 
}

But when I went to compile, as follows, I got the errors below --
although I thought I gave it the right type, namely char.

leslie:~/cprog$ gcc -o name name.c 
name.c: In function ‘main’: 
name.c:14: warning: format ‘%s’ expects type ‘char *’, but argument 2
has type ‘int’ 



********************
This is the relevant text from the Lesson:
> /* 
>    age; an example program showing 
>    the difference between puts and printf
> */
> 
> #include <stdio.h>
> 
> int main()
> {
>     int age;
> 
>     puts( "Please enter your age: " );
>     scanf( "%d", &age );
>     printf( "Wow, you are %d years old.\n", age);
> 
>     return 0;
> }
> 
> The output of this is nicely-formatted:
> 
> $ age
> Please enter your age: 
> 80
> Wow, you are 80 years old. 
> 
> There are a number of cool things happening in this tiny program: it asks for 
> input, we enter something, and then it uses it correctly in a sentence. The 
> scanf function scans and formats input, and printf formats output.  %d is a 
> placeholder, and it means scan an integer as a signed decimal number. A signed 
> integer can be either a negative or positive number; an unsigned integer is 
> only positive. 
> 
> scanf( "%d", &age ); means "read the user input and place that value into the 
> variable age." You must use the & symbol in front of your variable or it won't 
> work. If you want to jump ahead this is your introduction to using pointers, 
> which is pointing to a specific location on memory. Pointers is a weird and 
> complicated subject to explain, so for now I'm going to leave it at "don't 
> forget the & symbol when you're playing with scanf." (Anyone who wants to 
> chime in with their own explanation of pointers is welcome!)
> 
> scanf has already assigned the value of the user input to our age variable, so 
> all printf has to do is display it. 
> 
> Some other commonly-used scanf and printf placeholders are:
> 
>     %f -- float
>     %c -- single character
>     %s -- character strings
>     %i -- signed integer, or hexadecimal when preceded by 0x and octal when 
> preceded by 0
> 

>