I am trying to create an ELF file of my application which includes
  printf's,scanf's and file operations ,from arm-elf-gcc iam getting
  undefined symbol error during linking process,
  arm-elf-gcc -c source.c -o source.o  (no errors)
  arm-elf-ld -Ttext 0x100 -e 0x100 source.o -o source.elf (Undefined
  reference to printf...) 

      This is my source program-
                          I want to generate app.elf file for target
      cpu=arm7tdmi board

int main()
int i;

C:\armelf\bin>arm-elf-gcc -c -gstabs app.c -o app.o

C:\armelf\bin>arm-elf-ld -Ttext 0x100 -e 0x100 app.o -o app.elf
app.o(.text+0x1c): In function `main':
app.c:5: undefined reference to `scanf'
app.o(.text+0x28):app.c:6: undefined reference to `printf'