C :: How To Printf Floats

I am having a hard time with some of my homework, specifically regarding how to printf floats. I can't seem to print the number i want out using float, it just becomes a jumbled mess.

Code:
#include <stdio.h>
#define TICKER "LRCX"
#define PURCHASE_DATE "01/02/13"
#define SELL_DATE "01/30/13"
#define INVESTMENT_AMOUNT "10,000.00"

[Code] .....

Thats the code I currently have, I've probably tried everything to get the number to come out, but I just cant seem to figure it out. It should look like this, but with different numbers and stock:

Stock: MCD Buy Date: 01/02/13 Sell Date: 01/29/13 Buy Share Price: $89.40 Sell Share Price: $91.50 Shares Purchased: 111.86

Amount of Investment: $10,000.00 Value of Shares Sold: $10,234.90 Amount of Gain/Loss: $234.90 Percent Gain/Loss: 2.35%

However, this is how mine turns out:

Code::Blocks
Enter share purchase price for LRCX=>23
Enter the selling price for LRCX=>23

Stock: LRCX
Buy Date: 01/02/13
Sell Date: 01/30/13
Buy Share Price: -1.#R
Sell Share Price: -1.#R
Shares Purchased: -1.#R

Amount of Investment: 10,000.00
Value of Shares Sold:-1.#R
Amount of Gain/Loss:-1.#R
Percent Gain/Loss:-1.#R%

Process returned 0 (0x0) execution time : 2.864 s
Press any key to continue.