Header files and libraries (Kevin Lynch)

For more information, see nu32.org. This video is a supplement to the book "Embedded Computing and Mechatronics with the PIC32 Microcontroller," Lynch, Marchuk, and Elwin. It is part of Northwestern University's ME 333 Introduction to Mechatronics.
L-comp: Say you have a header file header.h, and inside it it has the statement
float HelperFloat;
Then this header is included by both file1.c and file2.c. These compile successfully to file1.o and file2.o. When these two codes are linked into a single executable, though, the linker fails. Explain why.