Diff function

data dm;
input X;
cards;
12.45
23.56
34.78
50.67
60.12
-12.34
9.0
;
data dm1;
set dm;
It=int(x);
R1=Round(x);
R2=Round(x,.1);
Ab=abs(x);
C=ceil(x);
F=floor(x);
lg1=log(x);
log10=log10(x);
m=mod(x,3);
run;
proc print data=dm1;
run;
data month_sales;
input month $ sale;
cards;
jan 450
feb 410
mar 420
apr 480
may 320
jun 340
;
data sale_dif;
set month_sales;
sdif=dif(sales);
if sdif='.' then sdif=o;
run;
proc print data=sale_dif;
run;