how to sum each previous rows

[Pato485]

Hello, i want to ask how can i sum each previous rows by variable SPCislo, here is sample of data:

PK	DatumPodpisu	SPcislo	cislo
501377324233203	23Sep2019 0:00:00,000	5100543	10
501377324233208	23Sep2019 0:00:00,000	5100543	10
501377324233213	23Sep2019 0:00:00,000	5100543	10
501377324274981	23Sep2019 0:00:00,000	5100543	10
501377324461518	10Mar2020 0:00:00,000	555	38,0352
501377324452148	11Mar2020 0:00:00,000	555	11,543
501377324458471	12Mar2020 0:00:00,000	555	195,7242

And i want to calculated sum of each row by rows group by SPCislo, like this:

PK	DatumPodpisu	SPcislo	cislo	how to calculate this???
501377324233203	23Sep2019 0:00:00,000	5100543	10	10
501377324233208	23Sep2019 0:00:00,000	5100543	10	20
501377324233213	23Sep2019 0:00:00,000	5100543	10	30
501377324274981	23Sep2019 0:00:00,000	5100543	10	40
501377324461518	10Mar2020 0:00:00,000	555	38,0352	38,0352
501377324452148	11Mar2020 0:00:00,000	555	11,543	49,5782
501377324458471	12Mar2020 0:00:00,000	555	195,7242	245,3024

Thanks all for help 🙂

[PeterClemmensen · Accepted solution]

data want;
   set have;
   by SPcislo;
   if first.SPcislo then c = 0;
   c + cislo;
run;

[Kurt_Bremser]

Or, very slightly optimized:

data want;
set have;
by SPcislo;
if first.SPcislo
then c = cislo;
else c + cislo;
run;

(at all FIRST. events, there's only one assignment instead of two)