memory location c8051f381

Your post doesn't make sense. It seems like you try to create two variables with the same name.

float EffectiveTime=0;
float EffectiveTime=0;

I only see one form - repeated twice?

And please follow the instructions on how to post source code - see the picture: www.danlhenry.com/.../keil_code.png

When I select the first option I have strange effects
Perhaps the memory overflow

1)

#include "compiler_defs.h"
#include "C8051F380_defs.h"                // SFR declarations
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <float.h>

#include "LCD_controll_M_40.c"
#include "Memory_mangment_M_40.c"
#include "rtc_controll_M_40.c"
.
.
.
float EffectiveTime=0;

.
.
.
void main (void)
{
.
.
.
.




}

2)

#include "compiler_defs.h"
#include "C8051F380_defs.h"                // SFR declarations
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <float.h>

#include "LCD_controll_M_40.c"
#include "Memory_mangment_M_40.c"
#include "rtc_controll_M_40.c"
.
.
.
float EffectiveTime;

.
.
.
void main (void)
{EffectiveTime=0;
..
}

so, your first post should have been:

Does it change the memory location following two forms of writing? float EffectiveTime=0; float EffectiveTime;

and the answer is: probably

it MAY be that the compiler bunches initialized variables separate from non-initialized.

anyhow, why do you care?

You're right I did not frame the question correctly
I would like to understand how memory works

I would like to understand how memory works
reading your question as is the answer is "you put data there to read it later"
I'm sure that is not your problem, but for "how memory works" I have no other answer